Various aspects of upper-limb muscle strength and tennis performance. A comparative study of U12 and U14 female tennis players

Various aspects of upper-limb muscle strength and tennis performance. 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A comparative study of U12 and U14 female tennis players Tomasz Waldziński, Aleksandra Durzyńska, Bartłomiej Niespodziński, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7895075/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study investigated the relationship between muscle strength and tennis performance, assessed using the International Tennis Number (ITN) protocol, in young female tennis players aged under 12 (U12) and under 14 (U14). Thirty-three players underwent a comprehensive evaluation including ITN testing, general strength tests (handgrip strength, flexed arm hang, and tennis-ball throw), isometric upper-limb muscle strength, and sense of force assessment. Results demonstrated significantly higher ITN scores and muscle strength in the U14 group, with differences largely attributable to body size and training experience. Correlation analyses revealed age-specific patterns: in U12 players, ITN scores were associated primarily with general strength measures, whereas in U14 players, they were more strongly linked to joint-specific upper-limb strength and neuromuscular characteristics. Sense of force did not differ between groups, though correlations with ITN varied depending on age and joint function. These findings suggest that, in this sample, performance in younger players was more closely associated with general strength measures, whereas in older players it was more closely associated with joint-specific upper-limb strength, underscoring the importance of adjusting training strategies to both the biological and technical stages of athletes. The results highlight the role of muscle strength not only in supporting general performance but also in refining technical execution in young female tennis players. Health sciences/Anatomy Health sciences/Health care Biological sciences/Physiology rate of torque development force reproduction glenohumeral joint elbow joint radiocarpal joint INTRODUCTION The International Tennis Number (ITN) protocol is a globally recognized tool for classifying and assessing tennis skills. This international ranking system provides an objective framework for evaluating and monitoring a player’s overall game development, using tennis-specific technical tasks such as ball control, accuracy, and stroke power 1 . The ITN scale comprises ten levels: ITN 1 identifies professional-level players, whereas ITN 10 corresponds to beginners. The system is employed both in player development and in the organization of competitive events, facilitating the matching of opponents with comparable playing standards 1 . Tennis performance, as reflected in ITN test outcomes, is determined by multiple factors 1 , 2 , 3 . Given the structure of the ITN protocol, it is reasonable to hypothesize that muscle strength, particularly of the upper limb, may exert a substantial influence on ITN scores and could even serve as a predictor of ranking. Muscle strength is a key neurophysiological component of tennis performance, defined as the capacity to execute technical and tactical tasks effectively under the sport’s specific demands 4 , 5 . It plays a pivotal role in generating stroke velocity and in enabling dynamic movement across the court. Moreover, greater strength contributes to speed, stability, and movement precision while reducing injury risk through improved body control and enhanced joint support 4 . Identifying the relationship between muscle strength and the level of expertise defined by ITN can provide valuable insights for coaches and players, highlighting which muscle strength aspects should be prioritized to optimize competitive performance 1 . Previous research confirms that muscle strength is a crucial determinant of tennis performance and is directly reflected in ITN scores 1 . For instance, players achieving higher ITN levels demonstrated greater explosive strength, reflected in significant correlations with vertical jump performance and overhead medicine-ball throw distance 1 . Moreover, it was demonstrated that athletes with greater lower-limb explosive strength achieved superior results in speed tests and generated significantly higher ball velocities during the serve—one of the key elements influencing ITN evaluation 6 . Likewise, players with greater trunk rotational strength have been shown to demonstrate superior stroke stabilization, which contributing to improved shot precision and directional control 7 . These findings are particularly relevant to the ITN protocol, which assesses, among other factors, the regularity and accuracy of strokes. Collectively, these findings suggest that muscle strength is one of the primary predictors of tennis performance when assessed using the ITN protocol. Nevertheless, few studies have specifically examined the relationship between tennis performance and muscle strength of the upper limbs. Understanding this association may provide a scientific basis for designing more effective tennis training programs that target the key physical parameters required to achieve higher ITN rankings. The development of muscle strength undergoes marked changes throughout ontogeny, reflecting not only biological maturation but also adaptations to external stimuli 8 , 9 . Although primarily determined by genetic factors, its development is strongly shaped by environmental influences—most notably by systematic sports training, which constitutes an integral component of high-performance tennis practice 10 . In girls, the development of strength capacities is particularly pronounced between the ages of 10 and 14 years 11 , 12 . During this maturational window, substantial gains occur in both muscle mass and neuromuscular coordination, providing the foundation for improvements across different manifestations of muscle strength. In accordance, a two-year longitudinal survey demonstrated that knee-extensor muscle strength in elite young tennis players increases markedly after the age of 13, especially in high-velocity movements 13 . Similarly, it was shown that around 12–13 years of age the development of force sense in young female tennis players approaches the level observed in older age groups, which may enhance tennis performance 14 . After this critical period, the rate of muscle-strength development in girls slows considerably 9 , 15 , 16 . Considering the role of muscle strength in tennis performance, gaining insight into the development of muscle strength and its relationship with tennis performance, expressed through the ITN scores, in young female players aged 10–14, may represent a turning point in the planning and optimizing training strategies. Therefore, the aim of the present study was twofold: (i) to compare multiple aspects of muscle strength between under-12 (U12) and under-14 (U14) female tennis players, and (ii) to evaluate the relationship between ITN score and various strength characteristics within these groups. METHODS Study design This cross-sectional study involved two groups of female tennis players U12 and U14 —who underwent a comprehensive assessment of tennis performance and selected indices of muscle strength. Performance was evaluated using the ITN protocol, while general muscle strength was examined through a handgrip strength test, a flexed arm hang test (FAH), and a tennis ball throw for distance test (TBT). In addition, isometric muscle strength and sense of force of the dominant upper limb were assessed. All procedures were conducted over two consecutive days in the Exercise Physiology Laboratory of the Gdańsk University of Physical Education and Sport, Gdańsk, Poland. Prior to testing, participants were familiarized with all procedures and, on both testing days, completed a standardized warm-up to optimize performance. On day 1, participants initially completed the isometric muscle strength assessment of the dominant upper limb. Following a one-hour recovery period, the sense of force test was administered to evaluate the accuracy of muscle strength perception and control. On day 2, the ITN test was administered to assess overall tennis performance. After a three-hour rest interval, participants completed, in sequence: TBT test, handgrip strength test, and FAH test. Short passive rest periods were provided between trials to ensure consistent and repeatable performance. Participants Recruitment took place during the preparatory training period. A total of 33 female tennis players were enrolled and stratified into two age categories: U12 and U14. Players were selected by their coaches from seven regional tennis clubs as the most talented athletes and were recruited on the basis of their tennis skills assessed by the ITN—with a minimum ITN of 8 for U12 and 6 for U14—and their tournament results, as reflected in official ranking lists. The detailed characteristics of the study groups are presented in Table 1 . Table 1 Characteristics of the participants (mean ± standard deviation) Variable U12 (n = 16) U14 (n = 17) t p Cohen’s d Chronological age (years) 11.35 ± 0.70 14.11 ± 0.82 10.35 < 0.01* 3.62 Body height (cm) 153.63 ± 8.75 163.59 ± 6.44 3.74 < 0.01* 1.29 Body mass (kg) 43.28 ± 7.25 51.58 ± 7.45 3.24 < 0.01* 1.12 Body Mass Index (kg⋅m − 1 ) 18.25 ± 2.09 19.20 ± 1.84 1.40 0.17 0.48 Training experience (years) 5.50 ± 0.62 7.56 ± 0.78 6.22 < 0.01* 2.92 Weekly training volume (hours) 6.90 ± 0.90 11.10 ± 0.80 9.48 < 0.01* 4.90 U12, U14, under & 12 or under &14 years of age respectively. *significant differences at p < 0.01 In addition to regular tennis training, all participants attended mandatory physical education classes (4 × 45 minutes per week). The study was conducted in accordance with the Declaration of Helsinki, and was approved by the Bioethics Committee for Clinical Research of the Regional Medical Association in Gdańsk, Poland (approval no. KB-25/20). Written informed consent was obtained from each participant and her legal guardians prior to study enrollment. Procedures International Tennis Number (ITN) The ITN is a globally recognized tennis-ranking system that provides an objective measure of a player’s overall playing level. It uses a 10-point scale, ranging from ITN 1 (highest playing standard) to ITN 10 (beginner). The ITN test was conducted on an indoor clay court. A professional coach with 25 years of experience served balls to the players during the test. The final ITN score is the sum of points obtained across five components: 1) groundstroke depth – 10 alternating forehand and backhand strokes from the baseline (maximum 90 points); 2) groundstroke accuracy – 6 alternating forehands and backhands down the line and 6 cross-court (maximum 84 points); 3) volley depth – 8 alternating forehand and backhand volleys (maximum 72 points); 4) serve – 12 serves, three to each designated target area (maximum 108 points); 5) mobility – a “spider run,” in which the player sprints around the court collecting five balls one at a time and placing them in a designated zone (maximum 76 points). The maximum overall score was 430 points. Testing was performed in accordance with the International Tennis Federation (ITF) guidelines 17 . For every stroke-based task (all except the mobility test), points were awarded for: shot accuracy, based on where the ball landed within the singles court; shot power, with one bonus point if the ball’s second bounce landed between the baseline and the “bonus line” and two bonus points if it landed beyond the bonus line; consistency, with one additional point for every shot executed without error. The total score across all tasks determined the player’s ITN skill level, in accordance with the official ITF classification standards described in the International Tennis Number: On-Court Assessment Guide, levels 4 and 5 17 . Handgrip strength test Maximal isometric handgrip strength was measured using an electronic hand dynamometer with Hercules software (Saehan Corporation, Masanhappo-gu Changwon, Republic of Korea). Each player performed three trials with the dominant hand; the highest value was used for analysis. Participants were seated comfortably with feet flat on the floor and the tested arm supported on a stable, flat surface. The shoulder was in a neutral position, the elbow flexed at 90°, and the wrist maintained at 0–30° of dorsiflexion. Before testing, the dynamometer was calibrated according to the manufacturer’s instructions to ensure measurement accuracy. Immediately prior to each trial, participants were instructed to hold the dynamometer so that the handle fit comfortably—not too tight or loose—grasping it with four fingers around the handle and the thumb positioned on the opposite side 18 . For each attempt, they were asked to squeeze the dynamometer as forcefully as possible for approximately 3–5 s, while receiving standardized verbal encouragement. A 1-minute rest interval between trials prevented muscular fatigue 19 . Results were expressed as absolute values and normalized to body mass. Flexed arm hang test The FAH was administered according to the Eurofit Test protocol in an indoor sports hall 20 . A horizontal bar (diameter ≤ 2.5 cm) was mounted at a height easily reachable by the participants. A protective gymnastics mat was placed underneath, and hand chalk was provided to improve grip. Timing was recorded with a digital stopwatch. Participants grasped the bar using a closed overhand grip at shoulder width, standing on a chair to assume the starting position. At the signal to start, the support was removed and the participant maintained a FAH with the chin held above the bar. Timing continued until the participant’s chin dropped below the level of the bar. The test was performed once, with time recorded to the nearest 0.01 s. Participants wore light sports clothing. Tennis-ball throw for distance test Upper-limb explosive strength was assessed by a TBT test for distance in an indoor sports hall. To eliminate the contribution of the lower limbs, the throw was performed from a half-kneeling position: right-handed players knelt with the left leg forward, and left-handed players with the right leg forward, maintaining an upright trunk. Holding a tennis ball at chest height with the dominant arm, participants executed a maximal forward overhead throw, generating force primarily through the shoulder girdle and trunk while maintaining the kneeling base position. Throw distance was measured in a straight line from the throwing line to the first point of ground contact of the ball, with 1 cm precision. Two official trials were performed after two practice throws; the best distance of the two official attempts was used for analysis. A trial was repeated if the participant lost balance, left the kneeling position, or involved the lower limbs during the throwing motion. Upper limb isometric muscle strength assessment Isometric strength testing was performed using a Biodex System 4 isokinetic dynamometer (Biodex Medical Systems, Inc., Shirley, NY, USA). Participants were seated on the dynamometer’s adjustable chair, and the backrest was individually positioned to fit each player’s body in accordance with the manufacturer’s guidelines. To ensure postural stabilization, leather straps were applied across the chest, pelvis, and thigh. Isometric assessments were conducted for three upper-limb joints: glenohumeral, elbow, and radiocarpal joints, each under standardized conditions. For the glenohumeral joint, the tested arm was abducted to 90° in the frontal plane with the elbow flexed to 90°. The hand was in a neutral grip on the dynamometer lever arm, and the device’s axis of rotation was aligned with the olecranon process. In this configuration, the muscle strength of external rotation (GHER) and internal rotation (GHIR) was assessed. For the elbow joint, the shoulder was flexed to 45°, with the entire upper limb supported by a pad beneath the olecranon process. The hand remained in a neutral position, and the dynamometer’s rotational axis was aligned with the lateral epicondyle of the humerus. This position allowed assessment of elbow flexion (EF) and elbow extension (EE) strength. Finally, for the radiocarpal joint, the forearm rested in pronation on a dedicated support. The dynamometer lever arm was positioned so that its axis of rotation was aligned with the ulnar styloid process. In this configuration, radiocarpal flexion (RCF) and radiocarpal extension (RCE) strength were evaluated. For each tested action, participants performed three maximal voluntary isometric contractions (MVICs). They were instructed to push or pull the limb segment as forcefully and as rapidly as possible, while receiving strong standardized verbal encouragement to elicit maximal effort. The trial with the highest peak torque (PT) was retained for analysis. For every joint action, the following variables were obtained: PT expressed in newton-meters (Nm), peak rate of torque development (PRTD) expressed in newton-meters per second (Nm·s⁻¹). Both PT and PRTD were normalized to body mass, yielding Nm·kg⁻¹ and Nm·s⁻¹·kg⁻¹, respectively. Sense of force testing This test was performed using the same dynamometer (Biodex System 4) and the identical joint positions as described in the upper-limb isometric muscle strength assessment. The joints and muscle actions evaluated were likewise the same as those assessed for isometric strength. The procedure consisted of ipsilateral reproduction of a memorized torque level under isometric conditions (torque reproduction test). Using visual feedback, each participant first observed on the dynamometer screen the target torque expressed as a percentage of the previously determined PT during MVIC for the specific joint and muscle action. After a 5-second rest period, she was asked to reproduce the same torque level without any visual or auditory feedback. Two target intensities, 20% and 50% of MVIC, were tested separately for each joint action. For each intensity, three trials were performed. The order of joints, muscle actions and target torque levels was randomized to minimize learning effects and fatigue. For the torque reproduction test, the primary outcome was the absolute error, calculated as the mean of the absolute differences (percentage points) between the target and reproduced torque values across all trials. Lower absolute error values indicated greater accuracy of torque reproduction. The reliability of force-sense assessment with the Biodex system has been previously established. In reference studies, the intraclass correlation coefficient (ICC) for the torque reproduction test reached 0.81 21 , indicating adequate methodological reliability. Statistical analysis All data are presented as mean ± standard deviation. Between-group differences were analyzed using independent-samples Student’s t-tests. For associations between individual muscle strength ITN scores, Pearson’s correlation coefficient (r) was calculated. The magnitude of effect size for differences and correlations were expressed as Cohen’s d, interpreted according to Cohen (1988) 22 and modified by Hopkins (2006) 23 as follows: small (d = 0.2–0.59; r = 0.10–0.29), moderate (d = 0.6–1.19; r = 0.30–0.49), large (d = 1.2–1.99; r = 0.50–0.69), and very large (d ≥ 2.0; r = 0.70–0.89). Before all analyses, assumptions of normality (Shapiro–Wilk test) and homogeneity of variance (Levene’s test) were verified, and no violations were found. Outliers exceeding three standard deviations from the mean were excluded. The level of statistical significance was set at α = 0.05. The required sample size for correlation analysis (n = 26) was estimated a priori using G*Power 3.1.9.4 (Franz Faul, Universität Kiel, Germany) for a large effect size and power = 0.80. For independent t-tests, the effective sample size was 24. All analyses were performed using Statistica 13.3 (TIBCO Software Inc., Palo Alto, CA, USA). RESULTS Across all ITN test components, the U14 female players outperformed the U12 group (Table 2 ). The mobility assessment was 34.7% higher in U14 (p < 0.01). Scores for groundstroke depth (38.6%, p < 0.01) and volley depth (42.7%, p < 0.01) were also significantly higher in U14 than in U12. In addition, U14 players demonstrated a significantly greater groundstroke accuracy score (54.0%, p < 0.01) and a higher serve score (31.7%, p < 0.01) compared with U12. The total ITN score was 39.4% higher in the U14 group (p < 0.01), whereas the corresponding ITN number was 32.0% lower (p < 0.01), indicating better overall tennis performance in the older players. Table 2 Tennis performance in International Tennis Number score (mean ± standard deviation) Variable U12 (n = 16) U14 (n = 17) t p Cohen’s d Groundstroke depth score 38.19 ± 15.92 52.94 ± 9.15 3.29 < 0.01** 1.15 Groundstroke accuracy score 32.00 ± 20.06 49.29 ± 17.06 2.67 0.01* 0.93 Volley depth score 20.00 ± 9.42 28.53 ± 9.27 2.62 0.01* 0.91 Serve score 44.81 ± 17.52 59.00 ± 15.12 2.49 0.02* 0.87 Mobility assessment score 30.88 ± 9.73 41.59 ± 6.91 3.66 < 0.01** 1.28 Sum of score 165.88 ± 59.89 231.35 ± 37.02 3.80 < 0.01** 1.32 International tennis number 6.75 ± 1.98 4.59 ± 1.12 -3.88 < 0.01** -1.35 U12, U14, under & 12 or under & 14 years of age, respectively. Significant differences at p *≤ 0.05, ** < 0.01 Significantly higher general muscle strength was observed in the U14 players compared with the U12 group (Table 3 ). Absolute handgrip strength was 28.0% higher (p < 0.01); however, when normalized to body mass, the difference was not statistically significant. FAH was 68.2% longer (p < 0.01), and TBT performance was 28.6% higher (p < 0.01) in U14 compared with U12. Table 3 General strength characteristics of the tennis players’ upper limbs (mean ± standard deviation) Variable U12 (n = 16) U14 (n = 17) t p Cohen’s d Hand grip strength (kg) 23.74 ± 4.11 30.40 ± 6.16 3.63 < 0.01** 1.26 Handgrip strength / body mass (N⋅kg − 1 ) 0.55 ± 0.07 0.59 ± 0.08 1.38 0.18 0.53 Flexed arm hang (s) 10.63 ± 8.81 17.87 ± 11.26 2.05 0.05* 0.71 Tennis ball throw (m) 15.69 ± 3.17 20.18 ± 4.40 3.34 < 0.01** 1.16 U12, U14, under & 12 or under & 14 years of age, respectively. Significant differences at p *≤ 0.05, ** < 0.01 U14 players exhibited significantly greater absolute PT across several joints and their respective muscle actions compared with the U12 group (Table 4 ). For GHIR, absolute PT was 23.1% higher (p < 0.05), with a trend toward a higher absolute PRTD (30.9%, p = 0.09). In GHER, absolute PT was 31.6% higher (p < 0.05), accompanied by a 32.7% higher absolute PRTD (p < 0.05). After normalization to body mass, these differences were not statistically significant. For EF, U14 players demonstrated a 29.3% higher absolute PT (p < 0.05) and a 20.3% higher absolute PRTD (p < 0.05) than U12, whereas in EE the differences were not significant. In the radiocarpal joint, no differences were observed between groups except for RCE, where U14 players showed significantly higher PRTD both in absolute terms (40.7%, p < 0.05) and when normalized to body mass (20.1%, p < 0.05). Table 4 Upper limb peak torque (PT) and peak rate torque development (PRTD) characteristics of the tennis players (mean ± standard deviation) Variable U12 (n = 16) U14 (n = 17) t p Cohen’s d Glenohumeral internal rotation PT (Nm) 17.15 ± 3.18 21.12 ± 4.96 2.50 0.02* 0.95 PT / body mass (Nm⋅kg − 1 ) 0.41 ± 0.08 0.42 ± 0.08 0.11 0.91 0.13 PRTD (Nm·s − 1 ) 142.24 ± 48.29 186.18 ± 90.18 1.73 0.09 0.6 PRTD / PT (Nm·s − 1 ·Nm − 1 ) 8.04 ± 2.63 7.75 ± 2.88 -0.29 0.77 -0.11 Glenohumeral external rotation PT (Nm) 17.98 ± 4.13 23.67 ± 6.44 3.00 0.01* 1.04 PT / body mass (Nm⋅kg − 1 ) 0.42 ± 0.11 0.46 ± 0.08 1.03 0.31 0.42 PRTD (Nm·s − 1 ) 323.89 ± 115.39 429.83 ± 158.46 2.18 0.04* 0.76 PRTD / PT (Nm·s − 1 ·Nm − 1 ) 18.30 ± 4.51 20.28 ± 5.01 1.19 0.24 0.41 Elbow flexion PT (Nm) 26.64 ± 5.58 34.44 ± 8.11 3.20 < 0.01** 1.11 PT / body mass (Nm⋅kg − 1 ) 0.62 ± 0.11 0.66 ± 0.10 1.21 0.24 0.38 PRTD (Nm·s − 1 ) 499.42 ± 130.25 600.82 ± 148.43 2.08 0.04* 0.72 PRTD / PT (Nm·s − 1 ·Nm − 1 ) 18.76 ± 2.91 17.67 ± 3.12 -1.04 0.31 -0.36 Elbow extension PT (Nm) 18.31 ± 6.51 20.95 ± 3.20 1.49 0.15 0.52 PT / body mass (Nm⋅kg − 1 ) 0.43 ± 0.15 0.41 ± 0.09 -0.32 0.75 -0.16 PKRTD (Nm·s − 1 ) 170.52 ± 86.00 202.90 ± 83.79 1.10 0.28 0.38 PRTD / PT (Nm·s − 1 ·Nm − 1 ) 9.36 ± 3.69 9.63 ± 3.48 0.21 0.83 0.08 Radiocarpal flexion PT (Nm) 7.62 ± 3.52 9.09 ± 3.97 1.13 0.27 0.39 PT / body mass (Nm⋅kg − 1 ) 0.17 ± 0.07 0.17 ± 0.06 -0.00 1.00 0.0 Absolute PRTD (Nm·s − 1 ) 49.77 ± 25.42 61.18 ± 24.00 61.18 0.19 0.46 PRTD / PT (Nm·s − 1 ·Nm − 1 ) 6.69 ± 1.18 6.87 ± 1.31 6.87 0.74 0.14 Radiocarpal extension PT (Nm) 5.16 ± 1.58 6.09 ± 1.57 1.70 0.10 0.59 PT / body mass (Nm⋅kg − 1 ) 0.12 ± 0.03 0.12 ± 0.03 -0.11 0.91 0.0 PRTD (Nm·s − 1 ) 54.18 ± 30.16 76.48 ± 33.49 2.01 0.05* 0.7 PRTD / PT (Nm·s − 1 ·Nm − 1 ) 10.08 ± 2.66 12.11 ± 3.02 2.04 0.04* 0.71 U12, U14, under & 12 or under & 14 years of age, respectively. Significant differences at p *≤ 0.05, ** < 0.01 No significant differences were observed between the U12 and U14 female players in torque reproduction test across the tested movements (Table 5 ). Table 5 Absolute error (percentage points) in torque reproduction test performance of the tennis players (mean ± standard deviation) Variable U12 (n = 16) U14 (n = 17) t p Cohen’s d Glenohumeral internal rotation 20% MVIC 4.64 ± 4.53 2.72 ± 1.77 -1.62 0.12 -0.57 50% MVIC 10.30 ± 7.97 10.93 ± 8.57 0.22 0.83 0.08 Glenohumeral external rotation 20% MVIC 3.82 ± 2.56 3.74 ± 2.47 -0.09 0.93 -0.03 50% MVIC 9.75 ± 7.54 6.82 ± 4.85 -1.34 0.19 -0.47 Elbow flexion 20% MVIC 3.27 ± 2.12 2.78 ± 1.75 -0.72 0.48 -0.25 50% MVIC 11.66 ± 7.07 9.67 ± 5.42 -0.91 0.37 -0.32 Elbow extention 20% MVIC 4.13 ± 3.81 3.20 ± 2.30 -0.86 0.40 -0.3 50% MVIC 10.19 ± 6.15 6.69 ± 4.25 -1.91 0.07 -0.67 Radiocarpal flexion 20% MVIC 3.45 ± 2.41 3.08 ± 2.47 -0.44 0.66 -0.15 50% MVIC 8.31 ± 6.07 6.86 ± 3.80 -0.83 0.42 -0.29 Radiocarpal extention 20% MVIC 3.89 ± 3.15 4.82 ± 4.27 0.71 0.48 0.25 50% MVIC 8.47 ± 4.77 6.39 ± 4.62 -1.27 0.21 -0.44 U12, U14, under & 12 or under & 14 years of age respectively; MVIC, maximal voluntary isometric contraction Pearson correlation analysis revealed significant associations between muscle strength and ITN test performance (Table 6 ). In the U12 female players, handgrip strength (r = 0.52–0.64), FAH test (r = 0.53–0.56), and TBT test performance (r = 0.52–0.78) were significantly correlated with groundstroke depth and accuracy scores. PT in EE—both in absolute terms (r = 0.64) and when normalized to body mass (r = 0.68)—also showed significant associations with groundstroke depth. In the U14 group, significant correlations were observed for absolute PT in GHIR (r = 0.48–0.59), as well as for the absolute PRTD (r = 0.67) and GHER (r = 0.53). For elbow function, absolute PT in EF (r = 0.54–0.65) and EE (r = 0.51) correlated with shot depth and accuracy. Additionally, in the U12 group, torque reproduction at 50% MVIC showed negative correlations with GHIR (r = − 0.58) and GHER (r = − 0.55). In the U14 group, torque reproduction at 20% MVIC exhibited positive correlations with EF and EE (r = 0.48–0.66). Table 6 Pearson’s correlation analysis of the International Tennis Number (ITN) and various muscle strength aspects Variable Groundstroke depth Groundstroke accuracy Volley depth Serve Mobility assessment ITN total score Handgrip strength Ns 0.52 (U14) Ns 0.64 (U14) Ns 0.63 (U14) Handgrip strength / BM 0.58 (U12) Ns Ns 0.58 (U14) 0.60 (U12) 0.55 (U12) Flexed arm hang 0.53 (U12) Ns Ns Ns 0.56 (U12) Ns Tennis ball throw 0.52 (U12) 0.78 (U12) Ns Ns 0.54 (U12) 0.66 (U12) Glenohumeral internal rotation PT 0.48 (U14) 0.58 (U14) Ns Ns Ns 0.59 (U14) PT / BM PT / BW Ns Ns Ns Ns Ns Ns PRTD Ns Ns Ns Ns Ns 0.67 (U14) PRTD / PT Ns Ns 0.51 (U14) Ns Ns Ns TR 20% MVIC Ns Ns Ns Ns Ns Ns TR 50% MVIC Ns Ns -0.58 (U12) Ns Ns Ns Glenohumeral external rotation PT Ns Ns Ns Ns Ns Ns PT / BM PT / BW Ns Ns Ns Ns Ns Ns PRTD Ns Ns Ns ns Ns 0.53 (U14) PRTD / PT Ns 0.57 (U14) Ns 0.50 (U14) Ns 0.62 (U14) TR 20% MVIC Ns -0.55 (U12) Ns Ns Ns Ns TR 50% MVIC Ns Ns Ns Ns Ns Ns Elbow flexion PT 0.54 (U14) 0.54 (U14) Ns Ns Ns 0.65 (U14) PT / BM Ns Ns Ns Ns Ns 0.49 (U14) PRTD Ns Ns Ns Ns Ns Ns PRTD / PT Ns Ns Ns Ns Ns Ns TR 20% MVIC Ns 0.52 (U14) Ns Ns 0.63 (U14) 0.66 (U14) TR 50% MVIC Ns Ns Ns Ns Ns Ns Elbow extension PT 0.51 (U14) Ns Ns Ns 0.64 (U12) Ns PT / BM Ns Ns Ns Ns 0.68 (U12) Ns PRTD Ns Ns Ns Ns Ns Ns PRTD / PT Ns Ns Ns Ns Ns Ns TR 20% MVIC Ns 0.48 (U14) Ns Ns Ns 0.53 (U14) TR 50% MVIC Ns Ns Ns Ns Ns Ns Radiocarpal flexion PT Ns Ns Ns Ns Ns Ns PT / BM Ns Ns Ns Ns Ns Ns PRTD Ns Ns Ns Ns Ns Ns PRTD / PT Ns Ns Ns Ns Ns 0.59 (U14) TR 20% MVIC Ns Ns 0.49 (U14) Ns Ns Ns TR 50% MVIC Ns Ns Ns Ns Ns Ns Radiocarpal extension PT 0.51 (U14) Ns Ns Ns 0.64 (U12) Ns PT / BM Ns Ns Ns Ns 0.68 (U12) Ns PRTD 0.51 (U14) 0.50 (U14) Ns Ns Ns Ns PRTD / PT Ns Ns Ns Ns 0.48 (U14) Ns TR 20% MVIC Ns Ns Ns Ns Ns Ns TR 50% MVIC Ns Ns Ns Ns Ns Ns MVIC, maximal voluntary isometric contraction; PT, peak torque; BM, body mass; PRTD, peak rate of torque development; TR, torque reproduction; U12, U14, under & 12 or under & 14 years of age respectively; TR: torque reproduction. All visible correlation coefficients are statistically significant at p ≤ 0.05; “Ns” indicates nonsignificant correlation. DISCUSSION The aim of the present study was to compare multiple aspects of muscle strength between U12 and U14 female tennis players in relation to their ITN scores. In this study U14 female players showed significantly higher ITN scores than U12 players, which is consistent with higher on-court performance in the older age category and with their longer playing experience 24 , 25 . Previous studies have shown that the most pronounced development in competitive tennis skills occurs between 10 and 14 years of age, a key period for optimizing training and identifying talent 7 , 24 , 25 . The ITN levels in our cohort (U12: 6.75; U14: 4.59) indicate a relatively high standard of competitive play, as players aged 13–14 years typically achieve ITN scores of approximately 3 to 6 depending on competitive level and training intensity 7 , 24 , 26 . ITN is a valuable tool for monitoring players’ progress and planning individualized training 1 , yet few studies have investigated its relationship with upper-limb muscle strength in young female athletes 27 . An adequate level of muscular strength constitutes the foundation for the execution of numerous technical skills, enabling more effective performance of strokes with a higher degree of difficulty, such as deep-court topspin shots or spin serves. This, in turn, translates into a greater tennis performance 3 , 28 , 29 . Systematic increases in training load during long-term training facilitate strength development, improve on-court movement and positively affect ITN scores 27 , as illustrated by the U12 and U14 players studied here. U14 players demonstrated significantly greater general muscle strength than U12 players, a difference mainly explained by their larger muscle mass after body-mass normalization of handgrip strength 30 . Comparable age-related increases have been observed in girls aged 11–16 years 31 . While Elliott et al. 31 found that higher tennis performance consistently coincided with greater overall strength, Ulbricht et al. 32 suggested that this link may be confined to U12 and U16 players, but not to U14. This indicates the possibility of differentiated relationships between strength and tennis performance in the U12 and U14 groups. A similar pattern was observed in the current study, where significant positive correlations between handgrip strength and ITN were found for groundstroke depth in the U12 group (only when normalized to body mass), while in the U14 group they concerned groundstroke accuracy and serve. This suggests that at this stage handgrip strength may constitute a limiting factor in the ability to execute strokes that allow the ball to reach adequate court depth. In the U14 group, where strength levels are already higher, the ability to precisely control ball trajectory and stabilize the racket becomes more important, which explains the emergence of correlations with accuracy and serve. It can therefore be assumed that with physical development, the role of general strength shifts from supporting power generation (depth) toward facilitating precise stroke control (accuracy, serve). These findings are consistent with previous studies 33 , 34 , which highlight significant correlations between handgrip strength and serve velocity in female players aged 12–14 years. In the present study, older female tennis players (U14) also demonstrated higher performance in functional strength tests, such as the FAH and the TBT. This finding is consistent with previous reports 32 , 35 . The relationship between the results of general muscle strength tests and the ITN components (primarily groundstroke depth) revealed exclusively positive correlations in the U12 group. This may be related to the fact that players in the U12 category are still characterized by a relatively low level of muscle strength at this age, which depends mainly on body mass (normalized handgrip strength, FAH test) rather than on developed neuromuscular coordination and the involvement of multiple joints within the kinematic chain (TBT test) 36 . The above findings appear to be supported by the positive correlations observed between the aforementioned muscle strength tests and the mobility assessment (exclusively in the U12 group), which primarily involves body displacement in an agility evaluation task. This is consistent with previous research 32 , where in tests not normalized by body mass (2-kg medicine ball throw), the effect size of correlations with tennis performance increased with age. Considering the total ITN score, positive correlations with absolute handgrip strength were again observed in the U14 group, while normalized values were associated in the U12 group. These results are consistent with other measures of tennis performance in female players aged 12–16, such as ranking position, where higher handgrip test scores were linked to better ranking outcomes 32 . It should be noted that ITN (r = 0.55–0.63) demonstrates a stronger association with muscle strength measured in this way compared to ranking (r = 0.19–0.30). Isometric muscle strength of the major upper limb joints was assessed together with general muscle strength. U14 players showed higher values than U12 players, and normalization indicated that these differences were mainly due to greater body mass. The study most likely showed a specific, targeted development of muscle strength in young female tennis players, as differences in maximal strength expressed as PT were found only in half of the analyzed joints and their functions, namely GHIR, GHER and EF. This pattern agrees with reports of a pronounced age-related increase in upper-limb muscle strength, particularly in the shoulder girdle and elbow flexors, associated with body-mass gains in young tennis players and other overhead athletes 35 , 37 , 38 . These findings point to the development of muscle strength specific to tennis strokes, especially in segments functionally essential for shot production. PRTD showed the same group differences as PT but was also higher for RCE. This applied to both absolute and body-mass-normalized values, indicating that the advantage in U14 players cannot be explained solely by greater muscle size or PT. It more likely reflects age- and training-related neuromuscular adaptations such as higher initial motor-unit discharge rates, improved synchronization and reduced electromechanical delay 39 , 40 . Tennis-specific practice may further enhance PRTD in RCE through increased tendon stiffness and refined intermuscular coordination 41 , 42 . These neuromuscular characteristics provide the physiological basis for how strength gains translate into on-court performance. Repeated stroke patterns at the shoulder and the acceleration during EF are essential for generating racket speed and spin to the ball 43 , 44 . A higher PRTD in EF indicates a greater capacity for rapid activation of the main agonists during the acceleration phase of the swing, a finding consistent with studies in young competitive players 45 . Analysis of the relationships between isometric muscle strength of individual joints and the ITN components reflecting technical skills (including groundstroke and volley) revealed significant positive correlations only in the U14 group. In U12 players, variables correlated mainly with the mobility assessment, confirming the previously described relationship between general strength and ITN. For groundstroke accuracy, PT correlated positively only with GHIR and EF. For groundstroke depth, significant positive correlations were observed for most joints and their functions except for GHER and RCF, which instead showed a significant correlation between normalized PRTD and total ITN total score. Such a pattern suggests that these functions play primarily a stabilizing and control role within the kinetic chain of the stroke: external shoulder rotation prepares the shoulder and positions the arm during the backswing, whereas RCF ensures precise racket orientation at ball contact. These results further indicate that the development of muscle strength in these joints supports the production of strokes of higher technical quality. Such relationships are consistent with the biomechanical model of the tennis stroke, in which both precise control of glenohumeral rotations and rapid acceleration of the distal segment of the upper limb are critical 45 , 46 , 47 . This is particularly evident in the long-term development of glenohumeral muscle strength, where GHIR progressively exceeds that of the antagonists 45 , 48 . While this adaptation reflects the progressive refinement of tennis performance, it simultaneously increases the risk of shoulder injury 37 , 45 . Most studies examining the relationship between joint muscle strength and tennis performance have focused on serve velocity, yet findings remain inconsistent: some report significant positive correlations with glenohumeral strength 28 , 47 , 49 , whereas others do not 27 . In the present study, although several upper-limb strength measures correlated with ITN components, serve performance itself showed no relationship with PT. This is not surprising given that serve velocity is typically assessed independently of the accuracy that contributes to the ITN score. By contrast, body-mass-normalized PRTD of GHER correlated positively with the serve component of ITN, suggesting that a higher PRTD may facilitate greater energy storage in the stretch–shortening cycle and thus enhance serve effectiveness 44 . This pattern differs from 47 , who reported strong associations between internal rotation strength and serve velocity for both PT and PRTD. Participants in that study (mean age 14.1 ± 1.2 years) had a higher ITN level (3), included both sexes, and served without the accuracy element considered in ITN scoring. These differences highlight that ITN should be interpreted not only as a final composite score but also with attention to the performance of its individual components. One of the few studies linking joint-specific muscle strength with the ITN is that of 27 , who found a positive correlation (r = 0.58) between isometric RCF and tennis performance. In the present study, PT of RCF showed no association with ITN, yet a similar correlation (r = 0.59) emerged for PRTD. It should be noted that 27 investigated boys who were older (17.0 ± 0.8 years) than the U14 category. The above observation is in line with the findings of Dobos et all. 50 , who reported a very strong positive relationship (r = 0.86) between rate of force development of the forearm muscles in handgrip strength testing and post-impact ball velocity of the flat serve in boys aged 14.8 ± 2.5 years. 50 emphasized that the rapid contraction of the wrist flexors allows the racket head to be positioned optimally immediately before ball contact, while relatively little force is produced during the remainder of the swing. Together these results underscore the functional importance of the ability to develop torque rapidly at the wrist for generating technically precise strokes. In summary of the muscle strength results, general strength tests (such as handgrip strength or hanging-from-bar test) provide a good representation of strength development; however, more detailed measurements, such as torque and the PRTD, may offer additional insights into the specificity of strength capacity development that is relevant for the training of young female tennis players. Finally, the study examined a proprioceptive aspect of muscle strength (sense of force) in form of the ability to reproduce torque, which is an essential element of motor control and an important determinant of stroke precision in tennis 51 , 52 . No significant differences in torque reproduction test were observed between U12 and U14 players across any tested joints or functions. Only EE at 50% of MVIC showed a trend (p = 0.07), suggesting a possible influence of training experience and maturation 53 , 54 . Studies in athletic populations have shown that better performance in torque reproduction test is typically associated with higher technical proficiency and greater training experience 14 . These results imply that the ability to reproduce muscle tension may develop before age 12 or that further differentiation occurs after age 14. The differences between U12 and U14 concerned not only individual upper-limb joints but also the very direction of the correlations. While smaller reproduction errors in U12 players were positively associated with groundstroke accuracy and volley depth, U14 players showed inverse correlations involving the elbow and radiocarpal joints. Such findings may reflect an indirect effect of PT, from which the 20% and 50% MVIC reproduction tasks were derived, rather than a direct relationship between torque reproduction test and ITN performance. Higher muscle strength has previously been linked to poorer torque reproduction accuracy, possibly due to the difficulty of estimating force when a larger motor-unit pool is recruited and to strength imbalances that compromise proprioception 55 , 56 . Notably, in U14 players significant correlations were limited to distal joints whose contribution to stroke generation is secondary to the trunk and shoulder 57 , 58 , 59 . Overall, the sense of force appears to play a different roles across age groups and is not a straightforward determinant of tennis performance, which depends on the integrated action of multiple segments of the kinetic chain rather than on the control of a single muscle group. In light of the above findings, it can be inferred that in younger age groups (U12), general strength capacities are the predominant factor influencing tennis performance, whereas in older players (U14), upper-limb specific strength indicators and neuromuscular control, directly related to the biomechanics of tennis strokes, become more important. This highlights the necessity of adjusting training to the athlete’s stage of biological and technical development. LIMITATIONS The main limitation of the study was that the pubertal stage and peak height velocity of the female tennis players were not assessed. It is possible that some of the observed effects were influenced by hormonal changes and maturation of the nervous system. However, a previous study on U13 and U15 female tennis players examined peri- and post–peak height velocity and reported no differences in body-mass-normalized muscle strength (Lopez-Valenciano et al., 2023). Moreover, in young tennis players aged 9–17 years, seasonal changes in neuromuscular performance were shown to be unaffected by maturation (Baiget et al., 2025). These observations suggest that maturation alone may not fully explain differences in strength when values are normalized to body mass. Nevertheless, because indices of maturation (eg, Tanner stage, peak height velocity) were not directly collected in the present study, and because neuromuscular development and hormonal status can affect both strength expression and on-court performance, we cannot isolate the independent contribution of maturation to the present results. The interpretation of the findings is further constrained by the cross-sectional design. The differences between U12 and U14 players should be understood as distinctions between two age categories within this specific sample, rather than confirmed longitudinal changes over time. As such, it is not possible to draw causal conclusions about how tennis performance or upper-limb strength develops with age or training exposure. Although most indicators of muscle strength were normalized to body mass, no multivariate analysis was performed to control simultaneously for potential confounders such as overall body size, limb length and leverage, training volume, or years of playing experience. This means that we cannot determine to what extent the observed differences reflect neuromuscular qualities versus anthropometric growth or accumulated practice. It should also be noted that the correlation analyses were based on relatively small group sizes (U12: n = 16; U14: n = 17). In addition, a large number of correlations were tested without formal adjustment for multiple comparisons, which increases the risk of type I error. The reported associations between specific strength characteristics and ITN components should therefore be regarded as exploratory and hypothesis-generating rather than definitive. While the ITN data were internally consistent, a larger sample would further strengthen the reliability and generalizability of these findings. It is also important to consider how tennis performance and strength were operationalized. Tennis performance was assessed using the ITN on-court evaluation, which emphasizes consistency, depth, accuracy, and mobility under standardized, coach-fed conditions. This approach does not fully capture match play demands such as tactical decision-making, adaptation to an unpredictable opponent, or isolated ball velocity. Finally, the players included in the present study were competitively trained, preselected young female athletes rather than a recreational or unselected junior population. Consequently, the applicability of these results is primarily limited to similarly trained female players of comparable competitive level and may not extend to boys or to less experienced athletes. CONCLUSIONS In this cohort of competitively trained young female tennis players, U14 athletes achieved higher total and subcomponent ITN scores than U12 athletes, indicating superior on-court performance in the older age category. The U14 group also showed higher values in most general strength tests (handgrip strength, flexed arm hang, and tennis ball throw) and in joint-specific upper-limb strength and rapid torque production at the shoulder, elbow and radiocarpal joints. When strength was normalized to body mass, many between-group differences in maximal torque were reduced, suggesting a substantial contribution of greater body size in the older players. No consistent differences were observed between groups in force reproduction accuracy. The relationship between strength and tennis performance differed between age categories. In U12 players, ITN outcomes were primarily associated with general strength indicators such as handgrip strength, flexed arm hang, and tennis ball throw distance, and these associations were most evident for components reflecting groundstroke depth, groundstroke accuracy and mobility. In U14 players, ITN outcomes were more closely related to joint-specific upper-limb strength and to the ability to generate torque rapidly in actions of the glenohumeral, elbow and radiocarpal joints. This pattern suggests that, within this sample, general upper-limb strength may contribute more directly to performance at younger ages, whereas more specific neuromuscular qualities of the shoulder, elbow and wrist appear increasingly relevant in older players, particularly for the control, placement and effectiveness of strokes. From a practical standpoint, these findings support the rationale for an age-appropriate approach to physical preparation in young female tennis players. At earlier stages, establishing a broad foundation of general upper-limb strength may help players achieve sufficient stroke depth and whole-court movement quality. With increasing training experience and competitive level, progressively greater emphasis may be placed on targeted joint-specific strength and on fast torque production in key segments of the hitting arm, with the aim of enhancing stroke stability, directional control and technical execution rather than only absolute power output. Declarations FUNDING This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Author Contribution TW - conceived and designed the study, coordinated data collection, performed the analyses, interpreted the results, drafted the manuscript and supervised the entire project and provided overall guidance.AD - contributed substantially to data acquisition, methodology development, literature review and critical revision of the manuscript.BN - contributed substantially to data acquisition, methodology development, literature review and critical revision of the manuscript.JM - contributed substantially to data acquisition, methodology development and critical revision of the manuscript.EP - contributed substantially to data acquisition and critical revision of the manuscript.AK- conceived and designed the study, coordinated data collection, performed the analyses, interpreted the results, drafted the manuscript and supervised the entire project and provided overall guidance.All authors reviewed and approved the final version of the manuscript and agreed to be accountable for all aspects of the work. ACKNOWLEDGEMENTS We gratefully acknowledge all participants who participated in this study for their cooperation and motivation. We also thank the Faculty of Physical Education, Gdańsk University of Physical Education and Sport for allowing us to use the Physiology Research Lab. Data Availability The data will be made publicly available once the scientific project to which they pertain has been completed. Interested researchers may contact the corresponding authors to discuss data access in compliance with applicable ethical and institutional guidelines. References Morais, J. E., Kilit, B., Arslan, E., Soylu, Y. & Neiva, H. P. Effects of a 6-week on-court training program on the International Tennis Number (ITN) and a range of physical fitness characteristics in young tennis players. Front. Sports Act. Living . 6 , 1304073. 10.3389/fspor.2024.1304073 (2024). Olcucu, B. & Vatansever, S. 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The effectiveness of proprioceptive training for improving motor function: a systematic review. Front. Hum. Neurosci. 8 , 1075. 10.3389/fnhum.2014.01075 (2014). Goble, D. J., Lewis, C. A., Hurvitz, E. A. & Brown, S. H. Development of upper limb proprioceptive accuracy in children and adolescents. Hum. Mov. Sci. 24 , 155–170. 10.1016/j.humov.2005.05.004 (2005). Niespodzinski, B. et al. Elbow Joint Position and Force Senses in Young and Adult Untrained People and Gymnasts. Int. J. Environ. Res. Public. Health . 19 10.3390/ijerph19137592 (2022). Kaynak, H., Altun, M. & Tok, S. Effect of Force Sense to Active Joint Position Sense and Relationships between Active Joint Position Sense, Force Sense, Jumping and Muscle Strength. J. Mot Behav. 52 , 342–351. 10.1080/00222895.2019.1627280 (2020). Altun, M. Effects of 2 Different External Loads on Joint Position Sense and the Relationship Between Muscle Strength and Force Sense. J. Sport Rehabil . 29 , 1115–1120. 10.1123/jsr.2019-0025 (2020). Kibler, W. B. & Safran, M. Tennis injuries. Med. Sport Sci. 48 , 120–137. 10.1159/000084285 (2005). Elliott, B., Reid, M. & Crespo, M. Biomechanics of Advanced Tennis . (2003). Kibler, W. B. The role of the scapula in athletic shoulder function. Am. J. Sports Med. 26 , 325–337. 10.1177/03635465980260022801 (1998). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7895075","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":549081380,"identity":"3a8582a0-db30-4c7a-b070-98d8c6459cbb","order_by":0,"name":"Tomasz 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16:10:39","extension":"html","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":228274,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7895075/v1/46ed13026c838f99cd749129.html"},{"id":99797409,"identity":"35e956cc-b808-4d8d-8035-05284cfe3323","added_by":"auto","created_at":"2026-01-08 13:45:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1382233,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7895075/v1/5f034f82-a9bc-4bda-9b43-84b9fee15958.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Various aspects of upper-limb muscle strength and tennis performance. A comparative study of U12 and U14 female tennis players","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe International Tennis Number (ITN) protocol is a globally recognized tool for classifying and assessing tennis skills. This international ranking system provides an objective framework for evaluating and monitoring a player\u0026rsquo;s overall game development, using tennis-specific technical tasks such as ball control, accuracy, and stroke power \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. The ITN scale comprises ten levels: ITN 1 identifies professional-level players, whereas ITN 10 corresponds to beginners. The system is employed both in player development and in the organization of competitive events, facilitating the matching of opponents with comparable playing standards \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTennis performance, as reflected in ITN test outcomes, is determined by multiple factors \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Given the structure of the ITN protocol, it is reasonable to hypothesize that muscle strength, particularly of the upper limb, may exert a substantial influence on ITN scores and could even serve as a predictor of ranking. Muscle strength is a key neurophysiological component of tennis performance, defined as the capacity to execute technical and tactical tasks effectively under the sport\u0026rsquo;s specific demands \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. It plays a pivotal role in generating stroke velocity and in enabling dynamic movement across the court. Moreover, greater strength contributes to speed, stability, and movement precision while reducing injury risk through improved body control and enhanced joint support \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIdentifying the relationship between muscle strength and the level of expertise defined by ITN can provide valuable insights for coaches and players, highlighting which muscle strength aspects should be prioritized to optimize competitive performance \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Previous research confirms that muscle strength is a crucial determinant of tennis performance and is directly reflected in ITN scores \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. For instance, players achieving higher ITN levels demonstrated greater explosive strength, reflected in significant correlations with vertical jump performance and overhead medicine-ball throw distance \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. Moreover, it was demonstrated that athletes with greater lower-limb explosive strength achieved superior results in speed tests and generated significantly higher ball velocities during the serve\u0026mdash;one of the key elements influencing ITN evaluation \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Likewise, players with greater trunk rotational strength have been shown to demonstrate superior stroke stabilization, which contributing to improved shot precision and directional control \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. These findings are particularly relevant to the ITN protocol, which assesses, among other factors, the regularity and accuracy of strokes. Collectively, these findings suggest that muscle strength is one of the primary predictors of tennis performance when assessed using the ITN protocol. Nevertheless, few studies have specifically examined the relationship between tennis performance and muscle strength of the upper limbs. Understanding this association may provide a scientific basis for designing more effective tennis training programs that target the key physical parameters required to achieve higher ITN rankings.\u003c/p\u003e\u003cp\u003eThe development of muscle strength undergoes marked changes throughout ontogeny, reflecting not only biological maturation but also adaptations to external stimuli \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Although primarily determined by genetic factors, its development is strongly shaped by environmental influences\u0026mdash;most notably by systematic sports training, which constitutes an integral component of high-performance tennis practice \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. In girls, the development of strength capacities is particularly pronounced between the ages of 10 and 14 years \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. During this maturational window, substantial gains occur in both muscle mass and neuromuscular coordination, providing the foundation for improvements across different manifestations of muscle strength. In accordance, a two-year longitudinal survey demonstrated that knee-extensor muscle strength in elite young tennis players increases markedly after the age of 13, especially in high-velocity movements \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Similarly, it was shown that around 12\u0026ndash;13 years of age the development of force sense in young female tennis players approaches the level observed in older age groups, which may enhance tennis performance \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. After this critical period, the rate of muscle-strength development in girls slows considerably \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eConsidering the role of muscle strength in tennis performance, gaining insight into the development of muscle strength and its relationship with tennis performance, expressed through the ITN scores, in young female players aged 10\u0026ndash;14, may represent a turning point in the planning and optimizing training strategies. Therefore, the aim of the present study was twofold: (i) to compare multiple aspects of muscle strength between under-12 (U12) and under-14 (U14) female tennis players, and (ii) to evaluate the relationship between ITN score and various strength characteristics within these groups.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy design\u003c/h2\u003e\u003cp\u003eThis cross-sectional study involved two groups of female tennis players U12 and U14 \u0026mdash;who underwent a comprehensive assessment of tennis performance and selected indices of muscle strength. Performance was evaluated using the ITN protocol, while general muscle strength was examined through a handgrip strength test, a flexed arm hang test (FAH), and a tennis ball throw for distance test (TBT). In addition, isometric muscle strength and sense of force of the dominant upper limb were assessed.\u003c/p\u003e\u003cp\u003eAll procedures were conducted over two consecutive days in the Exercise Physiology Laboratory of the Gdańsk University of Physical Education and Sport, Gdańsk, Poland. Prior to testing, participants were familiarized with all procedures and, on both testing days, completed a standardized warm-up to optimize performance.\u003c/p\u003e\u003cp\u003eOn day 1, participants initially completed the isometric muscle strength assessment of the dominant upper limb. Following a one-hour recovery period, the sense of force test was administered to evaluate the accuracy of muscle strength perception and control.\u003c/p\u003e\u003cp\u003eOn day 2, the ITN test was administered to assess overall tennis performance. After a three-hour rest interval, participants completed, in sequence: TBT test, handgrip strength test, and FAH test. Short passive rest periods were provided between trials to ensure consistent and repeatable performance.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eParticipants\u003c/h3\u003e\n\u003cp\u003eRecruitment took place during the preparatory training period. A total of 33 female tennis players were enrolled and stratified into two age categories: U12 and U14. Players were selected by their coaches from seven regional tennis clubs as the most talented athletes and were recruited on the basis of their tennis skills assessed by the ITN\u0026mdash;with a minimum ITN of 8 for U12 and 6 for U14\u0026mdash;and their tournament results, as reflected in official ranking lists. The detailed characteristics of the study groups are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCharacteristics of the participants (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eU12 (n\u0026thinsp;=\u0026thinsp;16)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eU14 (n\u0026thinsp;=\u0026thinsp;17)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003et\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohen\u0026rsquo;s d\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChronological age (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e11.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e14.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e10.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.62\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody height (cm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e153.63\u0026thinsp;\u0026plusmn;\u0026thinsp;8.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e163.59\u0026thinsp;\u0026plusmn;\u0026thinsp;6.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody mass (kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e43.28\u0026thinsp;\u0026plusmn;\u0026thinsp;7.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e51.58\u0026thinsp;\u0026plusmn;\u0026thinsp;7.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody Mass Index (kg\u0026sdot;m\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e18.25\u0026thinsp;\u0026plusmn;\u0026thinsp;2.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e19.20\u0026thinsp;\u0026plusmn;\u0026thinsp;1.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTraining experience (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e5.50\u0026thinsp;\u0026plusmn;\u0026thinsp;0.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e7.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.92\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWeekly training volume (hours)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e6.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e11.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.90\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eU12, U14, under \u0026amp; 12 or under \u0026amp;14 years of age respectively. *significant differences at p\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\u003cp\u003eIn addition to regular tennis training, all participants attended mandatory physical education classes (4 \u0026times; 45 minutes per week). The study was conducted in accordance with the Declaration of Helsinki, and was approved by the Bioethics Committee for Clinical Research of the Regional Medical Association in Gdańsk, Poland (approval no. KB-25/20). Written informed consent was obtained from each participant and her legal guardians prior to study enrollment.\u003c/p\u003e\n\u003ch3\u003eProcedures\u003c/h3\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003eInternational Tennis Number (ITN)\u003c/h2\u003e\u003cp\u003eThe ITN is a globally recognized tennis-ranking system that provides an objective measure of a player\u0026rsquo;s overall playing level. It uses a 10-point scale, ranging from ITN 1 (highest playing standard) to ITN 10 (beginner). The ITN test was conducted on an indoor clay court. A professional coach with 25 years of experience served balls to the players during the test. The final ITN score is the sum of points obtained across five components: 1) groundstroke depth \u0026ndash; 10 alternating forehand and backhand strokes from the baseline (maximum 90 points); 2) groundstroke accuracy \u0026ndash; 6 alternating forehands and backhands down the line and 6 cross-court (maximum 84 points); 3) volley depth \u0026ndash; 8 alternating forehand and backhand volleys (maximum 72 points); 4) serve \u0026ndash; 12 serves, three to each designated target area (maximum 108 points); 5) mobility \u0026ndash; a \u0026ldquo;spider run,\u0026rdquo; in which the player sprints around the court collecting five balls one at a time and placing them in a designated zone (maximum 76 points). The maximum overall score was 430 points. Testing was performed in accordance with the International Tennis Federation (ITF) guidelines \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. For every stroke-based task (all except the mobility test), points were awarded for: shot accuracy, based on where the ball landed within the singles court; shot power, with one bonus point if the ball\u0026rsquo;s second bounce landed between the baseline and the \u0026ldquo;bonus line\u0026rdquo; and two bonus points if it landed beyond the bonus line; consistency, with one additional point for every shot executed without error. The total score across all tasks determined the player\u0026rsquo;s ITN skill level, in accordance with the official ITF classification standards described in the International Tennis Number: On-Court Assessment Guide, levels 4 and 5 \u003csup\u003e17\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eHandgrip strength test\u003c/h3\u003e\n\u003cp\u003eMaximal isometric handgrip strength was measured using an electronic hand dynamometer with Hercules software (Saehan Corporation, Masanhappo-gu Changwon, Republic of Korea). Each player performed three trials with the dominant hand; the highest value was used for analysis. Participants were seated comfortably with feet flat on the floor and the tested arm supported on a stable, flat surface. The shoulder was in a neutral position, the elbow flexed at 90\u0026deg;, and the wrist maintained at 0\u0026ndash;30\u0026deg; of dorsiflexion. Before testing, the dynamometer was calibrated according to the manufacturer\u0026rsquo;s instructions to ensure measurement accuracy. Immediately prior to each trial, participants were instructed to hold the dynamometer so that the handle fit comfortably\u0026mdash;not too tight or loose\u0026mdash;grasping it with four fingers around the handle and the thumb positioned on the opposite side \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. For each attempt, they were asked to squeeze the dynamometer as forcefully as possible for approximately 3\u0026ndash;5 s, while receiving standardized verbal encouragement. A 1-minute rest interval between trials prevented muscular fatigue \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. Results were expressed as absolute values and normalized to body mass.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eFlexed arm hang test\u003c/h2\u003e\u003cp\u003eThe FAH was administered according to the Eurofit Test protocol in an indoor sports hall \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. A horizontal bar (diameter\u0026thinsp;\u0026le;\u0026thinsp;2.5 cm) was mounted at a height easily reachable by the participants. A protective gymnastics mat was placed underneath, and hand chalk was provided to improve grip. Timing was recorded with a digital stopwatch. Participants grasped the bar using a closed overhand grip at shoulder width, standing on a chair to assume the starting position. At the signal to start, the support was removed and the participant maintained a FAH with the chin held above the bar. Timing continued until the participant\u0026rsquo;s chin dropped below the level of the bar. The test was performed once, with time recorded to the nearest 0.01 s. Participants wore light sports clothing.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eTennis-ball throw for distance test\u003c/h3\u003e\n\u003cp\u003eUpper-limb explosive strength was assessed by a TBT test for distance in an indoor sports hall. To eliminate the contribution of the lower limbs, the throw was performed from a half-kneeling position: right-handed players knelt with the left leg forward, and left-handed players with the right leg forward, maintaining an upright trunk. Holding a tennis ball at chest height with the dominant arm, participants executed a maximal forward overhead throw, generating force primarily through the shoulder girdle and trunk while maintaining the kneeling base position. Throw distance was measured in a straight line from the throwing line to the first point of ground contact of the ball, with 1 cm precision. Two official trials were performed after two practice throws; the best distance of the two official attempts was used for analysis. A trial was repeated if the participant lost balance, left the kneeling position, or involved the lower limbs during the throwing motion.\u003c/p\u003e\n\u003ch3\u003eUpper limb isometric muscle strength assessment\u003c/h3\u003e\n\u003cp\u003eIsometric strength testing was performed using a Biodex System 4 isokinetic dynamometer (Biodex Medical Systems, Inc., Shirley, NY, USA). Participants were seated on the dynamometer\u0026rsquo;s adjustable chair, and the backrest was individually positioned to fit each player\u0026rsquo;s body in accordance with the manufacturer\u0026rsquo;s guidelines. To ensure postural stabilization, leather straps were applied across the chest, pelvis, and thigh. Isometric assessments were conducted for three upper-limb joints: glenohumeral, elbow, and radiocarpal joints, each under standardized conditions. For the glenohumeral joint, the tested arm was abducted to 90\u0026deg; in the frontal plane with the elbow flexed to 90\u0026deg;. The hand was in a neutral grip on the dynamometer lever arm, and the device\u0026rsquo;s axis of rotation was aligned with the olecranon process. In this configuration, the muscle strength of external rotation (GHER) and internal rotation (GHIR) was assessed. For the elbow joint, the shoulder was flexed to 45\u0026deg;, with the entire upper limb supported by a pad beneath the olecranon process. The hand remained in a neutral position, and the dynamometer\u0026rsquo;s rotational axis was aligned with the lateral epicondyle of the humerus. This position allowed assessment of elbow flexion (EF) and elbow extension (EE) strength. Finally, for the radiocarpal joint, the forearm rested in pronation on a dedicated support. The dynamometer lever arm was positioned so that its axis of rotation was aligned with the ulnar styloid process. In this configuration, radiocarpal flexion (RCF) and radiocarpal extension (RCE) strength were evaluated. For each tested action, participants performed three maximal voluntary isometric contractions (MVICs). They were instructed to push or pull the limb segment as forcefully and as rapidly as possible, while receiving strong standardized verbal encouragement to elicit maximal effort. The trial with the highest peak torque (PT) was retained for analysis. For every joint action, the following variables were obtained: PT expressed in newton-meters (Nm), peak rate of torque development (PRTD) expressed in newton-meters per second (Nm\u0026middot;s⁻\u0026sup1;). Both PT and PRTD were normalized to body mass, yielding Nm\u0026middot;kg⁻\u0026sup1; and Nm\u0026middot;s⁻\u0026sup1;\u0026middot;kg⁻\u0026sup1;, respectively.\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eSense of force testing\u003c/h2\u003e\u003cp\u003eThis test was performed using the same dynamometer (Biodex System 4) and the identical joint positions as described in the upper-limb isometric muscle strength assessment. The joints and muscle actions evaluated were likewise the same as those assessed for isometric strength. The procedure consisted of ipsilateral reproduction of a memorized torque level under isometric conditions (torque reproduction test). Using visual feedback, each participant first observed on the dynamometer screen the target torque expressed as a percentage of the previously determined PT during MVIC for the specific joint and muscle action. After a 5-second rest period, she was asked to reproduce the same torque level without any visual or auditory feedback. Two target intensities, 20% and 50% of MVIC, were tested separately for each joint action. For each intensity, three trials were performed. The order of joints, muscle actions and target torque levels was randomized to minimize learning effects and fatigue. For the torque reproduction test, the primary outcome was the absolute error, calculated as the mean of the absolute differences (percentage points) between the target and reproduced torque values across all trials. Lower absolute error values indicated greater accuracy of torque reproduction. The reliability of force-sense assessment with the Biodex system has been previously established. In reference studies, the intraclass correlation coefficient (ICC) for the torque reproduction test reached 0.81 \u003csup\u003e21\u003c/sup\u003e, indicating adequate methodological reliability.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eAll data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. Between-group differences were analyzed using independent-samples Student\u0026rsquo;s t-tests. For associations between individual muscle strength ITN scores, Pearson\u0026rsquo;s correlation coefficient (r) was calculated. The magnitude of effect size for differences and correlations were expressed as Cohen\u0026rsquo;s d, interpreted according to Cohen (1988) \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e and modified by Hopkins (2006) \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e as follows: small (d\u0026thinsp;=\u0026thinsp;0.2\u0026ndash;0.59; r\u0026thinsp;=\u0026thinsp;0.10\u0026ndash;0.29), moderate (d\u0026thinsp;=\u0026thinsp;0.6\u0026ndash;1.19; r\u0026thinsp;=\u0026thinsp;0.30\u0026ndash;0.49), large (d\u0026thinsp;=\u0026thinsp;1.2\u0026ndash;1.99; r\u0026thinsp;=\u0026thinsp;0.50\u0026ndash;0.69), and very large (d\u0026thinsp;\u0026ge;\u0026thinsp;2.0; r\u0026thinsp;=\u0026thinsp;0.70\u0026ndash;0.89). Before all analyses, assumptions of normality (Shapiro\u0026ndash;Wilk test) and homogeneity of variance (Levene\u0026rsquo;s test) were verified, and no violations were found. Outliers exceeding three standard deviations from the mean were excluded. The level of statistical significance was set at α\u0026thinsp;=\u0026thinsp;0.05. The required sample size for correlation analysis (n\u0026thinsp;=\u0026thinsp;26) was estimated a priori using G*Power 3.1.9.4 (Franz Faul, Universit\u0026auml;t Kiel, Germany) for a large effect size and power\u0026thinsp;=\u0026thinsp;0.80. For independent t-tests, the effective sample size was 24. All analyses were performed using Statistica 13.3 (TIBCO Software Inc., Palo Alto, CA, USA).\u003c/p\u003e\u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eAcross all ITN test components, the U14 female players outperformed the U12 group (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The mobility assessment was 34.7% higher in U14 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Scores for groundstroke depth (38.6%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and volley depth (42.7%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) were also significantly higher in U14 than in U12. In addition, U14 players demonstrated a significantly greater groundstroke accuracy score (54.0%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and a higher serve score (31.7%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) compared with U12. The total ITN score was 39.4% higher in the U14 group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), whereas the corresponding ITN number was 32.0% lower (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), indicating better overall tennis performance in the older players.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eTennis performance in International Tennis Number score (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eU12 (n\u0026thinsp;=\u0026thinsp;16)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eU14 (n\u0026thinsp;=\u0026thinsp;17)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003et\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohen\u0026rsquo;s d\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroundstroke depth score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e38.19\u0026thinsp;\u0026plusmn;\u0026thinsp;15.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e52.94\u0026thinsp;\u0026plusmn;\u0026thinsp;9.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt; 0.01**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroundstroke accuracy score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e32.00\u0026thinsp;\u0026plusmn;\u0026thinsp;20.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e49.29\u0026thinsp;\u0026plusmn;\u0026thinsp;17.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.93\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVolley depth score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e20.00\u0026thinsp;\u0026plusmn;\u0026thinsp;9.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e28.53\u0026thinsp;\u0026plusmn;\u0026thinsp;9.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.91\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eServe score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e44.81\u0026thinsp;\u0026plusmn;\u0026thinsp;17.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e59.00\u0026thinsp;\u0026plusmn;\u0026thinsp;15.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.02*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMobility assessment score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e30.88\u0026thinsp;\u0026plusmn;\u0026thinsp;9.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e41.59\u0026thinsp;\u0026plusmn;\u0026thinsp;6.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.28\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSum of score\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e165.88\u0026thinsp;\u0026plusmn;\u0026thinsp;59.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e231.35\u0026thinsp;\u0026plusmn;\u0026thinsp;37.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.32\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInternational tennis number\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e6.75\u0026thinsp;\u0026plusmn;\u0026thinsp;1.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e4.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-3.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt; 0.01**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e-1.35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eU12, U14, under \u0026amp; 12 or under \u0026amp; 14 years of age, respectively. Significant differences at p *\u0026le; 0.05, ** \u0026lt; 0.01\u003c/p\u003e\u003cp\u003eSignificantly higher general muscle strength was observed in the U14 players compared with the U12 group (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Absolute handgrip strength was 28.0% higher (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01); however, when normalized to body mass, the difference was not statistically significant. FAH was 68.2% longer (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and TBT performance was 28.6% higher (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) in U14 compared with U12.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eGeneral strength characteristics of the tennis players\u0026rsquo; upper limbs (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eU12 (n\u0026thinsp;=\u0026thinsp;16)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eU14 (n\u0026thinsp;=\u0026thinsp;17)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabc\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003et\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabd\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohen\u0026rsquo;s d\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHand grip strength (kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e23.74\u0026thinsp;\u0026plusmn;\u0026thinsp;4.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e30.40\u0026thinsp;\u0026plusmn;\u0026thinsp;6.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.26\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHandgrip strength / body mass (N\u0026sdot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e0.55\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e0.59\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.53\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFlexed arm hang (s)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e10.63\u0026thinsp;\u0026plusmn;\u0026thinsp;8.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e17.87\u0026thinsp;\u0026plusmn;\u0026thinsp;11.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.05*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.71\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTennis ball throw (m)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e15.69\u0026thinsp;\u0026plusmn;\u0026thinsp;3.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e20.18\u0026thinsp;\u0026plusmn;\u0026thinsp;4.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eU12, U14, under \u0026amp; 12 or under \u0026amp; 14 years of age, respectively. Significant differences at p *\u0026le; 0.05, ** \u0026lt; 0.01\u003c/p\u003e\u003cp\u003eU14 players exhibited significantly greater absolute PT across several joints and their respective muscle actions compared with the U12 group (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). For GHIR, absolute PT was 23.1% higher (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), with a trend toward a higher absolute PRTD (30.9%, p\u0026thinsp;=\u0026thinsp;0.09). In GHER, absolute PT was 31.6% higher (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), accompanied by a 32.7% higher absolute PRTD (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). After normalization to body mass, these differences were not statistically significant. For EF, U14 players demonstrated a 29.3% higher absolute PT (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and a 20.3% higher absolute PRTD (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) than U12, whereas in EE the differences were not significant. In the radiocarpal joint, no differences were observed between groups except for RCE, where U14 players showed significantly higher PRTD both in absolute terms (40.7%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and when normalized to body mass (20.1%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eUpper limb peak torque (PT) and peak rate torque development (PRTD) characteristics of the tennis players (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eU12 (n\u0026thinsp;=\u0026thinsp;16)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eU14 (n\u0026thinsp;=\u0026thinsp;17)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabe\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003et\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabf\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohen\u0026rsquo;s d\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eGlenohumeral internal rotation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabg\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT (Nm)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e17.15\u0026thinsp;\u0026plusmn;\u0026thinsp;3.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21.12\u0026thinsp;\u0026plusmn;\u0026thinsp;4.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.02*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabh\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / body mass (Nm\u0026sdot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e142.24\u0026thinsp;\u0026plusmn;\u0026thinsp;48.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e186.18\u0026thinsp;\u0026plusmn;\u0026thinsp;90.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD / PT (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026middot;Nm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.04\u0026thinsp;\u0026plusmn;\u0026thinsp;2.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.75\u0026thinsp;\u0026plusmn;\u0026thinsp;2.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.11\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eGlenohumeral external rotation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabi\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT (Nm)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e17.98\u0026thinsp;\u0026plusmn;\u0026thinsp;4.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.67\u0026thinsp;\u0026plusmn;\u0026thinsp;6.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.01*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.04\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabj\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / body mass (Nm\u0026sdot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e323.89\u0026thinsp;\u0026plusmn;\u0026thinsp;115.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e429.83\u0026thinsp;\u0026plusmn;\u0026thinsp;158.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.04*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.76\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD / PT (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026middot;Nm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e18.30\u0026thinsp;\u0026plusmn;\u0026thinsp;4.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.28\u0026thinsp;\u0026plusmn;\u0026thinsp;5.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.41\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eElbow flexion\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabk\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT (Nm)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e26.64\u0026thinsp;\u0026plusmn;\u0026thinsp;5.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e34.44\u0026thinsp;\u0026plusmn;\u0026thinsp;8.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.01**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.11\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabl\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / body mass (Nm\u0026sdot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e499.42\u0026thinsp;\u0026plusmn;\u0026thinsp;130.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e600.82\u0026thinsp;\u0026plusmn;\u0026thinsp;148.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.04*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.72\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD / PT (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026middot;Nm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e18.76\u0026thinsp;\u0026plusmn;\u0026thinsp;2.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e17.67\u0026thinsp;\u0026plusmn;\u0026thinsp;3.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-1.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.36\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eElbow extension\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabm\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT (Nm)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e18.31\u0026thinsp;\u0026plusmn;\u0026thinsp;6.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.95\u0026thinsp;\u0026plusmn;\u0026thinsp;3.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabn\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / body mass (Nm\u0026sdot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.41\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePKRTD (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e170.52\u0026thinsp;\u0026plusmn;\u0026thinsp;86.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e202.90\u0026thinsp;\u0026plusmn;\u0026thinsp;83.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD / PT (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026middot;Nm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9.36\u0026thinsp;\u0026plusmn;\u0026thinsp;3.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.63\u0026thinsp;\u0026plusmn;\u0026thinsp;3.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRadiocarpal flexion\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabo\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT (Nm)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.62\u0026thinsp;\u0026plusmn;\u0026thinsp;3.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.09\u0026thinsp;\u0026plusmn;\u0026thinsp;3.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabp\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / body mass (Nm\u0026sdot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbsolute PRTD (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e49.77\u0026thinsp;\u0026plusmn;\u0026thinsp;25.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e61.18\u0026thinsp;\u0026plusmn;\u0026thinsp;24.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e61.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD / PT (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026middot;Nm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.69\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.87\u0026thinsp;\u0026plusmn;\u0026thinsp;1.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRadiocarpal extension\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabq\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT (Nm)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.16\u0026thinsp;\u0026plusmn;\u0026thinsp;1.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.09\u0026thinsp;\u0026plusmn;\u0026thinsp;1.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.59\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabr\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / body mass (Nm\u0026sdot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.12\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e54.18\u0026thinsp;\u0026plusmn;\u0026thinsp;30.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e76.48\u0026thinsp;\u0026plusmn;\u0026thinsp;33.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.05*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePRTD / PT (Nm\u0026middot;s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026middot;Nm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10.08\u0026thinsp;\u0026plusmn;\u0026thinsp;2.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.11\u0026thinsp;\u0026plusmn;\u0026thinsp;3.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.04*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.71\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eU12, U14, under \u0026amp; 12 or under \u0026amp; 14 years of age, respectively. Significant differences at p *\u0026le; 0.05, ** \u0026lt; 0.01\u003c/p\u003e\u003cp\u003eNo significant differences were observed between the U12 and U14 female players in torque reproduction test across the tested movements (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAbsolute error (percentage points) in torque reproduction test performance of the tennis players (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eU12 (n\u0026thinsp;=\u0026thinsp;16)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eU14 (n\u0026thinsp;=\u0026thinsp;17)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabs\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003et\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabt\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ep\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohen\u0026rsquo;s d\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eGlenohumeral internal rotation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabu\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.64\u0026thinsp;\u0026plusmn;\u0026thinsp;4.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.72\u0026thinsp;\u0026plusmn;\u0026thinsp;1.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-1.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.57\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabv\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e50% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10.30\u0026thinsp;\u0026plusmn;\u0026thinsp;7.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10.93\u0026thinsp;\u0026plusmn;\u0026thinsp;8.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.08\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eGlenohumeral external rotation\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabw\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.82\u0026thinsp;\u0026plusmn;\u0026thinsp;2.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.74\u0026thinsp;\u0026plusmn;\u0026thinsp;2.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabx\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e50% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e9.75\u0026thinsp;\u0026plusmn;\u0026thinsp;7.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.82\u0026thinsp;\u0026plusmn;\u0026thinsp;4.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-1.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.47\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eElbow flexion\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taby\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabz\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.27\u0026thinsp;\u0026plusmn;\u0026thinsp;2.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.78\u0026thinsp;\u0026plusmn;\u0026thinsp;1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabaa\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e50% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11.66\u0026thinsp;\u0026plusmn;\u0026thinsp;7.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9.67\u0026thinsp;\u0026plusmn;\u0026thinsp;5.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.32\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eElbow extention\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabab\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.13\u0026thinsp;\u0026plusmn;\u0026thinsp;3.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.20\u0026thinsp;\u0026plusmn;\u0026thinsp;2.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabac\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e50% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10.19\u0026thinsp;\u0026plusmn;\u0026thinsp;6.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.69\u0026thinsp;\u0026plusmn;\u0026thinsp;4.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-1.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRadiocarpal flexion\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabad\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.45\u0026thinsp;\u0026plusmn;\u0026thinsp;2.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.08\u0026thinsp;\u0026plusmn;\u0026thinsp;2.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabae\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e50% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.31\u0026thinsp;\u0026plusmn;\u0026thinsp;6.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.86\u0026thinsp;\u0026plusmn;\u0026thinsp;3.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRadiocarpal extention\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabaf\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.89\u0026thinsp;\u0026plusmn;\u0026thinsp;3.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.82\u0026thinsp;\u0026plusmn;\u0026thinsp;4.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabag\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e50% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.47\u0026thinsp;\u0026plusmn;\u0026thinsp;4.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.39\u0026thinsp;\u0026plusmn;\u0026thinsp;4.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-1.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-0.44\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eU12, U14, under \u0026amp; 12 or under \u0026amp; 14 years of age respectively; MVIC, maximal voluntary isometric contraction\u003c/p\u003e\u003cp\u003ePearson correlation analysis revealed significant associations between muscle strength and ITN test performance (Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). In the U12 female players, handgrip strength (r\u0026thinsp;=\u0026thinsp;0.52\u0026ndash;0.64), FAH test (r\u0026thinsp;=\u0026thinsp;0.53\u0026ndash;0.56), and TBT test performance (r\u0026thinsp;=\u0026thinsp;0.52\u0026ndash;0.78) were significantly correlated with groundstroke depth and accuracy scores. PT in EE\u0026mdash;both in absolute terms (r\u0026thinsp;=\u0026thinsp;0.64) and when normalized to body mass (r\u0026thinsp;=\u0026thinsp;0.68)\u0026mdash;also showed significant associations with groundstroke depth. In the U14 group, significant correlations were observed for absolute PT in GHIR (r\u0026thinsp;=\u0026thinsp;0.48\u0026ndash;0.59), as well as for the absolute PRTD (r\u0026thinsp;=\u0026thinsp;0.67) and GHER (r\u0026thinsp;=\u0026thinsp;0.53). For elbow function, absolute PT in EF (r\u0026thinsp;=\u0026thinsp;0.54\u0026ndash;0.65) and EE (r\u0026thinsp;=\u0026thinsp;0.51) correlated with shot depth and accuracy. Additionally, in the U12 group, torque reproduction at 50% MVIC showed negative correlations with GHIR (r = \u0026minus;\u0026thinsp;0.58) and GHER (r = \u0026minus;\u0026thinsp;0.55). In the U14 group, torque reproduction at 20% MVIC exhibited positive correlations with EF and EE (r\u0026thinsp;=\u0026thinsp;0.48\u0026ndash;0.66).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePearson\u0026rsquo;s correlation analysis of the International Tennis Number (ITN) and various muscle strength aspects\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroundstroke depth\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eGroundstroke accuracy\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eVolley depth\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eServe\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabah\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMobility assessment\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eITN total score\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabai\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHandgrip strength\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.52 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.64 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.63 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eHandgrip strength / BM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.58 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.58 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.60 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.55 (U12)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eFlexed arm hang\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.53 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.56 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u003cp\u003eTennis ball throw\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.52 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.78 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.54 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.66 (U12)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eGlenohumeral internal rotation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabaj\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.48 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.58 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.59 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabak\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / BM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePT / BW\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.67 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD / PT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.51 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabal\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTR 20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTR 50% MVIC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-0.58 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eGlenohumeral external rotation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabam\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taban\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / BM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePT / BW\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ens\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.53 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD / PT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.57 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.50 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.62 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabao\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTR 20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-0.55 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTR 50% MVIC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eElbow flexion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabap\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.54 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.54 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.65 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabaq\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / BM\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.49 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD / PT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabar\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTR 20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.52 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.63 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.66 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTR 50% MVIC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eElbow extension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabas\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.51 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.64 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabat\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / BM\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.68 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD / PT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabau\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTR 20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.48 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.53 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTR 50% MVIC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eRadiocarpal flexion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabav\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabaw\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / BM\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD / PT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.59 (U14)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabax\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTR 20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.49 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTR 50% MVIC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eRadiocarpal extension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabay\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.51 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.64 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabaz\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePT / BM\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.68 (U12)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.51 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.50 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePRTD / PT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.48 (U14)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabba\" border=\"1\"\u003e\u003ccolgroup cols=\"1\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTR 20% MVIC\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTR 50% MVIC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eNs\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eMVIC, maximal voluntary isometric contraction; PT, peak torque; BM, body mass; PRTD, peak rate of torque development; TR, torque reproduction; U12, U14, under \u0026amp; 12 or under \u0026amp; 14 years of age respectively; TR: torque reproduction. All visible correlation coefficients are statistically significant at p\u0026thinsp;\u0026le;\u0026thinsp;0.05; \u0026ldquo;Ns\u0026rdquo; indicates nonsignificant correlation.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThe aim of the present study was to compare multiple aspects of muscle strength between U12 and U14 female tennis players in relation to their ITN scores. In this study U14 female players showed significantly higher ITN scores than U12 players, which is consistent with higher on-court performance in the older age category and with their longer playing experience \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Previous studies have shown that the most pronounced development in competitive tennis skills occurs between 10 and 14 years of age, a key period for optimizing training and identifying talent \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The ITN levels in our cohort (U12: 6.75; U14: 4.59) indicate a relatively high standard of competitive play, as players aged 13\u0026ndash;14 years typically achieve ITN scores of approximately 3 to 6 depending on competitive level and training intensity \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. ITN is a valuable tool for monitoring players\u0026rsquo; progress and planning individualized training \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, yet few studies have investigated its relationship with upper-limb muscle strength in young female athletes \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAn adequate level of muscular strength constitutes the foundation for the execution of numerous technical skills, enabling more effective performance of strokes with a higher degree of difficulty, such as deep-court topspin shots or spin serves. This, in turn, translates into a greater tennis performance \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. Systematic increases in training load during long-term training facilitate strength development, improve on-court movement and positively affect ITN scores \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, as illustrated by the U12 and U14 players studied here.\u003c/p\u003e\u003cp\u003eU14 players demonstrated significantly greater general muscle strength than U12 players, a difference mainly explained by their larger muscle mass after body-mass normalization of handgrip strength \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Comparable age-related increases have been observed in girls aged 11\u0026ndash;16 years \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. While Elliott et al. \u003csup\u003e31\u003c/sup\u003e found that higher tennis performance consistently coincided with greater overall strength, Ulbricht et al. \u003csup\u003e32\u003c/sup\u003e suggested that this link may be confined to U12 and U16 players, but not to U14. This indicates the possibility of differentiated relationships between strength and tennis performance in the U12 and U14 groups. A similar pattern was observed in the current study, where significant positive correlations between handgrip strength and ITN were found for groundstroke depth in the U12 group (only when normalized to body mass), while in the U14 group they concerned groundstroke accuracy and serve. This suggests that at this stage handgrip strength may constitute a limiting factor in the ability to execute strokes that allow the ball to reach adequate court depth. In the U14 group, where strength levels are already higher, the ability to precisely control ball trajectory and stabilize the racket becomes more important, which explains the emergence of correlations with accuracy and serve. It can therefore be assumed that with physical development, the role of general strength shifts from supporting power generation (depth) toward facilitating precise stroke control (accuracy, serve). These findings are consistent with previous studies \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e, which highlight significant correlations between handgrip strength and serve velocity in female players aged 12\u0026ndash;14 years. In the present study, older female tennis players (U14) also demonstrated higher performance in functional strength tests, such as the FAH and the TBT. This finding is consistent with previous reports \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe relationship between the results of general muscle strength tests and the ITN components (primarily groundstroke depth) revealed exclusively positive correlations in the U12 group. This may be related to the fact that players in the U12 category are still characterized by a relatively low level of muscle strength at this age, which depends mainly on body mass (normalized handgrip strength, FAH test) rather than on developed neuromuscular coordination and the involvement of multiple joints within the kinematic chain (TBT test) \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. The above findings appear to be supported by the positive correlations observed between the aforementioned muscle strength tests and the mobility assessment (exclusively in the U12 group), which primarily involves body displacement in an agility evaluation task. This is consistent with previous research \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e, where in tests not normalized by body mass (2-kg medicine ball throw), the effect size of correlations with tennis performance increased with age. Considering the total ITN score, positive correlations with absolute handgrip strength were again observed in the U14 group, while normalized values were associated in the U12 group. These results are consistent with other measures of tennis performance in female players aged 12\u0026ndash;16, such as ranking position, where higher handgrip test scores were linked to better ranking outcomes \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. It should be noted that ITN (r\u0026thinsp;=\u0026thinsp;0.55\u0026ndash;0.63) demonstrates a stronger association with muscle strength measured in this way compared to ranking (r\u0026thinsp;=\u0026thinsp;0.19\u0026ndash;0.30).\u003c/p\u003e\u003cp\u003eIsometric muscle strength of the major upper limb joints was assessed together with general muscle strength. U14 players showed higher values than U12 players, and normalization indicated that these differences were mainly due to greater body mass. The study most likely showed a specific, targeted development of muscle strength in young female tennis players, as differences in maximal strength expressed as PT were found only in half of the analyzed joints and their functions, namely GHIR, GHER and EF. This pattern agrees with reports of a pronounced age-related increase in upper-limb muscle strength, particularly in the shoulder girdle and elbow flexors, associated with body-mass gains in young tennis players and other overhead athletes \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. These findings point to the development of muscle strength specific to tennis strokes, especially in segments functionally essential for shot production.\u003c/p\u003e\u003cp\u003ePRTD showed the same group differences as PT but was also higher for RCE. This applied to both absolute and body-mass-normalized values, indicating that the advantage in U14 players cannot be explained solely by greater muscle size or PT. It more likely reflects age- and training-related neuromuscular adaptations such as higher initial motor-unit discharge rates, improved synchronization and reduced electromechanical delay \u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. Tennis-specific practice may further enhance PRTD in RCE through increased tendon stiffness and refined intermuscular coordination \u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. These neuromuscular characteristics provide the physiological basis for how strength gains translate into on-court performance. Repeated stroke patterns at the shoulder and the acceleration during EF are essential for generating racket speed and spin to the ball \u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. A higher PRTD in EF indicates a greater capacity for rapid activation of the main agonists during the acceleration phase of the swing, a finding consistent with studies in young competitive players \u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eAnalysis of the relationships between isometric muscle strength of individual joints and the ITN components reflecting technical skills (including groundstroke and volley) revealed significant positive correlations only in the U14 group. In U12 players, variables correlated mainly with the mobility assessment, confirming the previously described relationship between general strength and ITN. For groundstroke accuracy, PT correlated positively only with GHIR and EF. For groundstroke depth, significant positive correlations were observed for most joints and their functions except for GHER and RCF, which instead showed a significant correlation between normalized PRTD and total ITN total score. Such a pattern suggests that these functions play primarily a stabilizing and control role within the kinetic chain of the stroke: external shoulder rotation prepares the shoulder and positions the arm during the backswing, whereas RCF ensures precise racket orientation at ball contact.\u003c/p\u003e\u003cp\u003eThese results further indicate that the development of muscle strength in these joints supports the production of strokes of higher technical quality. Such relationships are consistent with the biomechanical model of the tennis stroke, in which both precise control of glenohumeral rotations and rapid acceleration of the distal segment of the upper limb are critical \u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e,\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e,\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. This is particularly evident in the long-term development of glenohumeral muscle strength, where GHIR progressively exceeds that of the antagonists \u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e,\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. While this adaptation reflects the progressive refinement of tennis performance, it simultaneously increases the risk of shoulder injury \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eMost studies examining the relationship between joint muscle strength and tennis performance have focused on serve velocity, yet findings remain inconsistent: some report significant positive correlations with glenohumeral strength \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e,\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e, whereas others do not \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. In the present study, although several upper-limb strength measures correlated with ITN components, serve performance itself showed no relationship with PT. This is not surprising given that serve velocity is typically assessed independently of the accuracy that contributes to the ITN score. By contrast, body-mass-normalized PRTD of GHER correlated positively with the serve component of ITN, suggesting that a higher PRTD may facilitate greater energy storage in the stretch\u0026ndash;shortening cycle and thus enhance serve effectiveness \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. This pattern differs from \u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e, who reported strong associations between internal rotation strength and serve velocity for both PT and PRTD. Participants in that study (mean age 14.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2 years) had a higher ITN level (3), included both sexes, and served without the accuracy element considered in ITN scoring. These differences highlight that ITN should be interpreted not only as a final composite score but also with attention to the performance of its individual components.\u003c/p\u003e\u003cp\u003eOne of the few studies linking joint-specific muscle strength with the ITN is that of \u003csup\u003e27\u003c/sup\u003e, who found a positive correlation (r\u0026thinsp;=\u0026thinsp;0.58) between isometric RCF and tennis performance. In the present study, PT of RCF showed no association with ITN, yet a similar correlation (r\u0026thinsp;=\u0026thinsp;0.59) emerged for PRTD. It should be noted that \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e investigated boys who were older (17.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8 years) than the U14 category. The above observation is in line with the findings of Dobos et all. \u003csup\u003e50\u003c/sup\u003e, who reported a very strong positive relationship (r\u0026thinsp;=\u0026thinsp;0.86) between rate of force development of the forearm muscles in handgrip strength testing and post-impact ball velocity of the flat serve in boys aged 14.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5 years. \u003csup\u003e50\u003c/sup\u003e emphasized that the rapid contraction of the wrist flexors allows the racket head to be positioned optimally immediately before ball contact, while relatively little force is produced during the remainder of the swing. Together these results underscore the functional importance of the ability to develop torque rapidly at the wrist for generating technically precise strokes. In summary of the muscle strength results, general strength tests (such as handgrip strength or hanging-from-bar test) provide a good representation of strength development; however, more detailed measurements, such as torque and the PRTD, may offer additional insights into the specificity of strength capacity development that is relevant for the training of young female tennis players.\u003c/p\u003e\u003cp\u003eFinally, the study examined a proprioceptive aspect of muscle strength (sense of force) in form of the ability to reproduce torque, which is an essential element of motor control and an important determinant of stroke precision in tennis \u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e,\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. No significant differences in torque reproduction test were observed between U12 and U14 players across any tested joints or functions. Only EE at 50% of MVIC showed a trend (p\u0026thinsp;=\u0026thinsp;0.07), suggesting a possible influence of training experience and maturation \u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e,\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e. Studies in athletic populations have shown that better performance in torque reproduction test is typically associated with higher technical proficiency and greater training experience \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. These results imply that the ability to reproduce muscle tension may develop before age 12 or that further differentiation occurs after age 14.\u003c/p\u003e\u003cp\u003eThe differences between U12 and U14 concerned not only individual upper-limb joints but also the very direction of the correlations. While smaller reproduction errors in U12 players were positively associated with groundstroke accuracy and volley depth, U14 players showed inverse correlations involving the elbow and radiocarpal joints. Such findings may reflect an indirect effect of PT, from which the 20% and 50% MVIC reproduction tasks were derived, rather than a direct relationship between torque reproduction test and ITN performance. Higher muscle strength has previously been linked to poorer torque reproduction accuracy, possibly due to the difficulty of estimating force when a larger motor-unit pool is recruited and to strength imbalances that compromise proprioception \u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e,\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. Notably, in U14 players significant correlations were limited to distal joints whose contribution to stroke generation is secondary to the trunk and shoulder \u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e,\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e,\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. Overall, the sense of force appears to play a different roles across age groups and is not a straightforward determinant of tennis performance, which depends on the integrated action of multiple segments of the kinetic chain rather than on the control of a single muscle group.\u003c/p\u003e\u003cp\u003eIn light of the above findings, it can be inferred that in younger age groups (U12), general strength capacities are the predominant factor influencing tennis performance, whereas in older players (U14), upper-limb specific strength indicators and neuromuscular control, directly related to the biomechanics of tennis strokes, become more important. This highlights the necessity of adjusting training to the athlete\u0026rsquo;s stage of biological and technical development.\u003c/p\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003eLIMITATIONS\u003c/h2\u003e\u003cp\u003eThe main limitation of the study was that the pubertal stage and peak height velocity of the female tennis players were not assessed. It is possible that some of the observed effects were influenced by hormonal changes and maturation of the nervous system. However, a previous study on U13 and U15 female tennis players examined peri- and post\u0026ndash;peak height velocity and reported no differences in body-mass-normalized muscle strength (Lopez-Valenciano et al., 2023). Moreover, in young tennis players aged 9\u0026ndash;17 years, seasonal changes in neuromuscular performance were shown to be unaffected by maturation (Baiget et al., 2025). These observations suggest that maturation alone may not fully explain differences in strength when values are normalized to body mass. Nevertheless, because indices of maturation (eg, Tanner stage, peak height velocity) were not directly collected in the present study, and because neuromuscular development and hormonal status can affect both strength expression and on-court performance, we cannot isolate the independent contribution of maturation to the present results.\u003c/p\u003e\u003cp\u003eThe interpretation of the findings is further constrained by the cross-sectional design. The differences between U12 and U14 players should be understood as distinctions between two age categories within this specific sample, rather than confirmed longitudinal changes over time. As such, it is not possible to draw causal conclusions about how tennis performance or upper-limb strength develops with age or training exposure.\u003c/p\u003e\u003cp\u003eAlthough most indicators of muscle strength were normalized to body mass, no multivariate analysis was performed to control simultaneously for potential confounders such as overall body size, limb length and leverage, training volume, or years of playing experience. This means that we cannot determine to what extent the observed differences reflect neuromuscular qualities versus anthropometric growth or accumulated practice. It should also be noted that the correlation analyses were based on relatively small group sizes (U12: n\u0026thinsp;=\u0026thinsp;16; U14: n\u0026thinsp;=\u0026thinsp;17). In addition, a large number of correlations were tested without formal adjustment for multiple comparisons, which increases the risk of type I error. The reported associations between specific strength characteristics and ITN components should therefore be regarded as exploratory and hypothesis-generating rather than definitive. While the ITN data were internally consistent, a larger sample would further strengthen the reliability and generalizability of these findings.\u003c/p\u003e\u003cp\u003eIt is also important to consider how tennis performance and strength were operationalized. Tennis performance was assessed using the ITN on-court evaluation, which emphasizes consistency, depth, accuracy, and mobility under standardized, coach-fed conditions. This approach does not fully capture match play demands such as tactical decision-making, adaptation to an unpredictable opponent, or isolated ball velocity.\u003c/p\u003e\u003cp\u003eFinally, the players included in the present study were competitively trained, preselected young female athletes rather than a recreational or unselected junior population. Consequently, the applicability of these results is primarily limited to similarly trained female players of comparable competitive level and may not extend to boys or to less experienced athletes.\u003c/p\u003e\u003c/div\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eIn this cohort of competitively trained young female tennis players, U14 athletes achieved higher total and subcomponent ITN scores than U12 athletes, indicating superior on-court performance in the older age category. The U14 group also showed higher values in most general strength tests (handgrip strength, flexed arm hang, and tennis ball throw) and in joint-specific upper-limb strength and rapid torque production at the shoulder, elbow and radiocarpal joints. When strength was normalized to body mass, many between-group differences in maximal torque were reduced, suggesting a substantial contribution of greater body size in the older players. No consistent differences were observed between groups in force reproduction accuracy.\u003c/p\u003e\u003cp\u003eThe relationship between strength and tennis performance differed between age categories. In U12 players, ITN outcomes were primarily associated with general strength indicators such as handgrip strength, flexed arm hang, and tennis ball throw distance, and these associations were most evident for components reflecting groundstroke depth, groundstroke accuracy and mobility. In U14 players, ITN outcomes were more closely related to joint-specific upper-limb strength and to the ability to generate torque rapidly in actions of the glenohumeral, elbow and radiocarpal joints. This pattern suggests that, within this sample, general upper-limb strength may contribute more directly to performance at younger ages, whereas more specific neuromuscular qualities of the shoulder, elbow and wrist appear increasingly relevant in older players, particularly for the control, placement and effectiveness of strokes.\u003c/p\u003e\u003cp\u003eFrom a practical standpoint, these findings support the rationale for an age-appropriate approach to physical preparation in young female tennis players. At earlier stages, establishing a broad foundation of general upper-limb strength may help players achieve sufficient stroke depth and whole-court movement quality. With increasing training experience and competitive level, progressively greater emphasis may be placed on targeted joint-specific strength and on fast torque production in key segments of the hitting arm, with the aim of enhancing stroke stability, directional control and technical execution rather than only absolute power output.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFUNDING\u003c/h2\u003e\u003cp\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eTW - conceived and designed the study, coordinated data collection, performed the analyses, interpreted the results, drafted the manuscript and supervised the entire project and provided overall guidance.AD - contributed substantially to data acquisition, methodology development, literature review and critical revision of the manuscript.BN - contributed substantially to data acquisition, methodology development, literature review and critical revision of the manuscript.JM - contributed substantially to data acquisition, methodology development and critical revision of the manuscript.EP - contributed substantially to data acquisition and critical revision of the manuscript.AK- conceived and designed the study, coordinated data collection, performed the analyses, interpreted the results, drafted the manuscript and supervised the entire project and provided overall guidance.All authors reviewed and approved the final version of the manuscript and agreed to be accountable for all aspects of the work.\u003c/p\u003e\u003ch2\u003eACKNOWLEDGEMENTS\u003c/h2\u003e\u003cp\u003eWe gratefully acknowledge all participants who participated in this study for their cooperation and motivation. We also thank the Faculty of Physical Education, Gdańsk University of Physical Education and Sport for allowing us to use the Physiology Research Lab.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data will be made publicly available once the scientific project to which they pertain has been completed. Interested researchers may contact the corresponding authors to discuss data access in compliance with applicable ethical and institutional guidelines.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMorais, J. E., Kilit, B., Arslan, E., Soylu, Y. \u0026amp; Neiva, H. P. Effects of a 6-week on-court training program on the International Tennis Number (ITN) and a range of physical fitness characteristics in young tennis players. \u003cem\u003eFront. Sports Act. 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Thirty-three players underwent a comprehensive evaluation including ITN testing, general strength tests (handgrip strength, flexed arm hang, and tennis-ball throw), isometric upper-limb muscle strength, and sense of force assessment. Results demonstrated significantly higher ITN scores and muscle strength in the U14 group, with differences largely attributable to body size and training experience. Correlation analyses revealed age-specific patterns: in U12 players, ITN scores were associated primarily with general strength measures, whereas in U14 players, they were more strongly linked to joint-specific upper-limb strength and neuromuscular characteristics. Sense of force did not differ between groups, though correlations with ITN varied depending on age and joint function. These findings suggest that, in this sample, performance in younger players was more closely associated with general strength measures, whereas in older players it was more closely associated with joint-specific upper-limb strength, underscoring the importance of adjusting training strategies to both the biological and technical stages of athletes. The results highlight the role of muscle strength not only in supporting general performance but also in refining technical execution in young female tennis players.\u003c/p\u003e","manuscriptTitle":"Various aspects of upper-limb muscle strength and tennis performance. A comparative study of U12 and U14 female tennis players","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-25 16:10:35","doi":"10.21203/rs.3.rs-7895075/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"41eb884e-dc24-4e14-886a-2c97db102dc2","owner":[],"postedDate":"November 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":58428089,"name":"Health sciences/Anatomy"},{"id":58428090,"name":"Health sciences/Health care"},{"id":58428091,"name":"Biological sciences/Physiology"}],"tags":[],"updatedAt":"2026-01-07T17:38:59+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-25 16:10:35","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7895075","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7895075","identity":"rs-7895075","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}