Isokinetic strength characteristics of trunk rotation and knee joint in female amateur boxers: asymmetry and implications for injury prevention

Isokinetic strength characteristics of trunk rotation and knee joint in female amateur boxers: asymmetry and implications for injury prevention | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Isokinetic strength characteristics of trunk rotation and knee joint in female amateur boxers: asymmetry and implications for injury prevention Yang Liu, Jian Xiao, Zhiyong Chen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9121035/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Objective: To investigate the asymmetry in trunk axial rotation and knee joint isokinetic strength characteristics among adolescent amateur female boxing athletes, providing guidance for sport-specific strength training and injury prevention. Methods: Sixteen adolescent amateur female boxing athletes [age 16.8 ± 1.8 years, height 168.2 ± 5.3 cm, body mass 59.7 ± 7.7 kg] were tested using the IsoMed 2000 isokinetic dynamometer. Knee joint concentric (CON) and eccentric (ECC) contractions, as well as trunk rotation concentric contractions, were assessed at angular velocities of 60°/s, 120°/s, and 180°/s, with 3 sets of 7 repetitions per velocity. Paired-samples t-tests were used to compare bilateral differences, and repeated-measures ANOVA was applied to evaluate velocity effects. Results: Trunk rotation concentric contractions exhibited significant velocity dependence and lateral asymmetry. Repeated-measures ANOVA revealed a significant main effect of velocity (P < 0.001). At 120°/s and 180°/s, left rotation (dominant side) showed significantly higher PT and TW compared to right rotation (P < 0.01, Cohen's d_z medium to large), whereas no significant difference was observed at the slower velocity of 60°/s. Knee joint eccentric strength was significantly greater than concentric strength (P < 0.001). In ECC mode, right-side flexor group PT and TW were significantly higher than the left side (P < 0.01), with a significant main effect of velocity (P < 0.001). In CON mode, parameters peaked at 60°/s and decreased significantly with increasing velocity (P 0.05), but in ECC mode, the left side was significantly higher than the right (P right) and knee joint muscle strength (ECC right flexors > left), with stronger performance on the dominant side. These imbalances may elevate the risk of lumbar and knee injuries. Compared with similar studies on amateur boxers, lower limb absolute strength appears relatively low in the present cohort. It is recommended to implement balanced bilateral trunk rotational training, strengthen rapid force production in the non-dominant side, and optimize the H/Q ratio to enhance sport-specific performance and reduce injury risk. isokinetic strength trunk rotation knee joint asymmetry female boxing injury prevention H/Q ratio Figures Figure 1 Figure 2 Introduction Punching power in boxing primarily originates from lower limb drive, with efficient momentum transfer to the upper limbs achieved through knee joint flexion-extension and hip/trunk rotation ( 1 ) ( 2 ) Lower limb initiation, core trunk transmission efficiency, and upper-lower limb coordination are critical determinants of punch timing, force output, and overall performance. Therefore, a systematic evaluation of knee joint and trunk rotational muscle strength characteristics in boxers is of significant importance for optimizing sport-specific strength training and preventing injuries. Isokinetic dynamometry ( 3 , 4 ) is widely regarded as the gold standard for assessing single-joint muscle group strength. By automatically adjusting resistance according to joint angular velocity, it enables precise measurement of peak torque (PT), total work (TW) throughout the full range of motion, while distinguishing between concentric (CON) and eccentric (ECC) contraction modes ( 5 , 6 ). Isokinetic devices are extensively used in athlete strength profiling, fatigue induction, and injury rehabilitation, particularly for analyzing velocity-dependent strength and muscle group balance (e.g., hamstring-to-quadriceps [H/Q] ratio) ( 7 ). Recent isokinetic strength studies in boxers have primarily focused on the knee and shoulder rotator muscle groups ( 8 ). For instance, Chen et al. ( 9 ) reported that knee extensor strength in amateur boxers is significantly correlated with elite-level performance, and bilateral asymmetry or abnormal H/Q ratios may increase the risk of knee injuries ( 10 ). Tasiopoulos et al. identified associations between shoulder rotator strength asymmetry and boxing performance ( 11 ), yet trunk rotation was not addressed. Trunk axial rotation constitutes a key link in the boxing punching kinetic chain, contributing 37.2–45.0% to punch force generation ( 2 ). However, isokinetic assessments of trunk rotation remain scarce and are more commonly reported in unilateral-dominant sports such as tennis and golf ( 12 ). Existing literature indicates that combat sport athletes frequently exhibit rotational muscle asymmetry (dominant side > non-dominant side), likely resulting from prolonged unilateral technical training, which may compromise lumbar stability and elevate injury risk ( 13 ). Notably, research on female and adolescent boxers is scarce. Available isokinetic knee data predominantly derive from adult male or mixed-sex samples ( 14 ). In female amateur and adolescent populations, muscle strength characteristics during developmental stages, bilateral asymmetry, and H/Q ratios may exhibit distinct patterns that are closely linked to injury susceptibility ( 15 ). Moreover, no systematic studies have yet integrated concentric/eccentric knee testing with concentric trunk rotation assessments while emphasizing asymmetry analysis. In light of these gaps, the present study employed the IsoMed 2000 isokinetic dynamometer to evaluate knee concentric/eccentric and trunk rotation concentric strength (at 60°/s, 120°/s, and 180°/s) in adolescent amateur female boxers (national level 1 or 2). The investigation systematically examined bilateral strength characteristics, asymmetry patterns, and H/Q ratios, with the aim of elucidating muscle strength profiles in this population and providing evidence-based guidance for balanced sport-specific training and injury prevention. 1 Subjects and Data Processing 1.1 Subjects Sixteen female boxing athletes from the Competitive Sports School of Shanghai University of Sport (coded as boxer01 to boxer16) participated in the study. All subjects adopted an orthodox stance (left foot forward) and were right-handed. They underwent isokinetic testing of the knee joint at various angular velocities in both eccentric and concentric modes, as well as concentric trunk rotation strength assessments. Prior to formal testing, basic anthropometric and training-related information was collected. The following measurements were recorded: training experience, age, height, body mass, BMI, waist circumference, hip circumference, waist-to-hip ratio, limb segment lengths, thigh circumference, and calf length. The group characteristics were as follows (mean ± SD): Age: 16.82 ± 1.83 years Training experience: 3.45 ± 1.86 years Height: 168.18 ± 5.30 cm Body mass: 59.73 ± 7.67 kg Waist-to-hip ratio: 0.80 ± 0.025 BMI: 21.06 ± 1.98 kg/m² Thigh circumference: 54.46 ± 2.84 cm Calf length: 37.91 ± 2.77 cm A priori power analysis was conducted for the paired-samples t-test (left vs. right side comparison) using G*Power 3.1.9.2 software ( 16 ). Parameters were set as follows: expected effect size Cohen's d_z = 0.5 (medium effect, representing the minimum clinically meaningful difference), two-tailed α = 0.05, and desired statistical power (1-β) = 0.95. The analysis indicated that a minimum sample size of n = 16 was required (achieved power = 0.955). In the actual study, observed effect sizes ranged from medium to large (Cohen's d = 0.5–1.37), confirming that the sample size was sufficient to detect true differences with adequate statistical power. 1.2 Data Processing All data are presented as mean ± standard deviation (Mean ± SD). Prior to statistical analysis, the normality of distribution was assessed using the Shapiro-Wilk test, and homogeneity of variances was evaluated with Levene’s test. For bilateral comparisons (left vs. right rotation / left vs. right knee), paired-samples t-tests were employed when data met the assumption of normality; otherwise, the non-parametric Wilcoxon signed-rank test was applied. Comparisons across different angular velocities were performed using repeated-measures analysis of variance (repeated measures ANOVA). When the assumption of sphericity was violated (Mauchly’s test, P < 0.05), degrees of freedom were corrected using either the Greenhouse-Geisser or Huynh-Feldt epsilon adjustment, as appropriate. Post-hoc pairwise comparisons were conducted with Bonferroni correction to control for multiple comparisons. Effect sizes were reported using Cohen’s d_z for paired comparisons, with the following interpretive guidelines: d_z = 0.2 (small), 0.5 (medium), and 0.8 (large).The significance level was set at α = 0.05 (two-tailed) for all tests. All statistical analyses were conducted using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). 2 Data Collection 2.1 Testing Procedure The IsoMed 2000 isokinetic testing system was powered on and calibrated. The dynamometer head was rotated 180° around the chair to initiate automatic startup of the main console screen. Each of the 16 athletes was assigned a unique identifier (boxer01 to boxer16). In the patient interface, basic information—including athlete code, date of birth, height, body mass, and other relevant details—was entered and saved. To retrieve or edit an athlete’s profile or select testing protocols, the corresponding athlete number was entered directly into the system. After retrieving the athlete’s information and exiting via the ESC key, the main testing interface was accessed. From the drop-down menu under test items, “Knee” or “Back” was selected and confirmed with the Enter key. “R” or “L” indicated right or left knee, respectively. In the movement mode interface, concentric (CON) or eccentric (ECC) testing was selected as M1 (flexion) or M2 (extension) actions. For concentric testing, identical contraction directions were chosen bilaterally (M1 CON, M2 CON); for eccentric testing, the corresponding modes were M1 ECC and M2 ECC. Angular velocities were set at 60°/s, 120°/s, and 180°/s, with 3 sets of 7 repetitions per velocity, an inter-set rest interval of 1 minute, and gravity compensation activated. Knee joint isokinetic strength testing The adjustable chair was configured with a backrest angle of 75° and a seat slide position of 12 mm forward. The athlete was seated in the appropriate position, and the dynamometer head height was adjusted. The infrared alignment marker was centered over the lateral femoral condyle to ensure accurate joint axis alignment. The shank was aligned parallel to the lever arm and secured just proximal to the ankle joint using straps. The upper body was stabilized with shoulder pads, and a wide waist belt was fastened around the pelvis. Both hands rested naturally on the side handles. The range of motion was set to 15°–105° (or 90° excursion, locked via button controls). During testing, the lever arm returned to the initial horizontal position, followed by a countdown. Prior to formal testing, athletes performed 3 submaximal familiarization trials at each target velocity while visually tracking the real-time torque feedback line on the monitor screen. Verbal encouragement was provided to ensure they reached the target line. Formal testing proceeded at 60°/s, 120°/s, and 180°/s, with 7 maximal repetitions per velocity. The highest peak torque and peak power values were recorded for analysis. Trunk rotation isokinetic strength testing The dynamometer head was connected to the trunk rotation attachment. Athletes were seated with the knees secured using the adjustable knee fixation buttons to achieve comfortable, pain-free lower limb stabilization. The shoulder pads were adjusted for optimal comfort and secure fixation. The lever arm began in the initial leftward position, followed by a countdown. Before formal testing, athletes completed 3 submaximal familiarization trials at each target velocity, again tracking the on-screen torque cue line with verbal encouragement to reach the designated threshold. Formal testing was conducted at 60°/s, 120°/s, and 180°/s, with 7 maximal repetitions per velocity. Peak torque, total work, and other relevant parameters were recorded. Athletes were instructed to refrain from fatiguing training the day prior to testing. All participants read and signed an informed consent form before commencement. Each testing session was preceded by a 15-minute standardized warm-up. If any discomfort or issue arose during testing, the athlete was instructed to verbally signal “stop,” upon which the experimenter immediately activated the emergency red stop button. Testing was scheduled across multiple days to minimize fatigue effects, particularly from eccentric contractions: Day 1: Left knee concentric testing Day 2: Right knee concentric testing Day 3: Left knee eccentric testing Day 4: Right knee eccentric testing Day 5: Trunk rotation testing Knee joint testing followed an alternating-day protocol, with concentric assessments performed first, followed by eccentric assessments on subsequent days, to prevent carry-over fatigue from eccentric loading (see Fig. 2 ). 2.2 Selected Parameters The following isokinetic strength parameters were selected for analysis: 1) Peak Torque (PT).Peak torque represents the highest torque value recorded on the torque curve during each repetition. It is expressed in Newton-meters (N·m) and serves as the primary indicator of maximal muscle strength under isokinetic conditions. 2) Hamstring-to-Quadriceps Ratio (H/Q ratio).The H/Q ratio is calculated as the ratio of hamstring (flexor) peak torque to quadriceps (extensor) peak torque, expressed as a percentage (%). This index reflects the strength balance between agonist and antagonist muscle groups surrounding the knee joint. A marked imbalance in this ratio may compromise joint stability and increase the risk of injury, particularly to the anterior cruciate ligament and other knee structures. 3) Total Work (TW) .Total work is defined as the cumulative area under the torque-time curve across the 7 repetitions of each set, representing the total mechanical work performed by the flexor and extensor muscle groups during the test. It is expressed in Joules (J) and provides an indirect measure of muscular endurance capacity. Clarification of Flexion and Extension Actions Eccentric (ECC) mode.The lever arm returns to the initial horizontal (extended) position at the start of the test. For eccentric quadriceps contraction (M2 ECC): The athlete resists the machine-driven flexion of the knee by eccentrically contracting the quadriceps while the lever arm moves downward.For eccentric hamstring contraction (M1 ECC): The athlete resists the machine-driven extension of the knee by eccentrically contracting the hamstrings as the lever arm moves upward to the extended position. Concentric (CON) mode.The lever arm also returns to the initial horizontal (extended) position at the start of the test. For concentric hamstring contraction (M1 CON): The athlete actively flexes the knee, concentrically contracting the hamstrings to pull the lever arm downward. For concentric quadriceps contraction (M2 CON): The athlete actively extends the knee, concentrically contracting the quadriceps to push the lever arm upward to the extended position. In both modes, the dynamometer provides matching resistance throughout the entire range of motion, ensuring constant angular velocity. 3 Results and Analysis 3.1 Analysis of Trunk Rotation Isokinetic Strength As shown in Table 1 (Trunk Rotation Peak Torque Statistics), at the slow velocity of 60°/s, peak torque (PT) of the left rotation muscle group was slightly higher than that of the right rotation group [86.39 ± 19.95 N·m vs. 82.24 ± 19.94 N·m], but the difference was not statistically significant (P = 0.154). At 120°/s, left rotation peak torque was significantly greater than right rotation [110.30 ± 21.37 N·m vs. 99.72 ± 18.18 N·m; paired t-test, t = 3.21, P = 0.006, Cohen’s d_z = 0.802]. Similarly, at 180°/s, the left-side advantage remained significant [77.15 ± 28.97 N·m vs. 62.03 ± 23.58 N·m; t = 3.45, P = 0.003, Cohen’s d_z = 0.862]. Repeated-measures analysis of variance (Repeated Measures ANOVA) revealed a significant main effect of velocity on total work (TW) [F(1.45, 21.75) = 28.74, P < 0.001, partial η² = 0.66], indicating a substantial overall difference in trunk rotational work output across angular velocities. Bonferroni post-hoc pairwise comparisons showed that total work at both 120°/s and 180°/s was significantly lower than at 60°/s (P 0.05). In summary, concentric trunk rotation peak torque and relative torque exhibit clear velocity-dependent and lateral asymmetry characteristics. At slow speeds, bilateral values are comparable, whereas at moderate-to-high velocities the left rotation (dominant side) advantage becomes markedly pronounced, with effect sizes ranging from medium to large. These findings suggest that the functional superiority of the dominant (left-rotating) muscle group is particularly evident during explosive force production and high-velocity endurance tasks. Table 1 Trunk Rotation Peak Torque Statistics (Unit: N·m) Testing Mode Angular Velocity Right Rotation Muscle Group Left Rotation Muscle Group P-value Concentric 60°/s 82.24 ± 19.94 86.39 ± 19.95 0.154 120°/s 99.72 ± 18.18 110.30 ± 21.37 0.006* 180°/s 62.03 ± 23.58 77.15 ± 28.97 0.003* Note: indicates statistical significance at P < 0.01. 3.1 Analysis of Trunk Rotation Isokinetic Strength (continued) As presented in Table 2 (Trunk Rotation Total Work Statistics), total work (TW) reflects the cumulative mechanical work performed across the seven repetitions and serves as an indirect indicator of muscular endurance capacity. The results demonstrated that at the moderate velocity of 120°/s, total work of the left rotation muscle group was significantly greater than that of the right rotation group [418.758 ± 74.26 J vs. 355.36 ± 78.85 J; paired t-test, P = 0.001, Cohen’s d_z = 0.93]. This indicates superior power output and work capacity of the left (dominant) rotators at this velocity. At the high velocity of 180°/s, the bilateral difference in total work remained highly significant (left rotation: 284.73 ± 98.29 J vs. right rotation: 228.12 ± 78.02 J; P = 0.001, Cohen’s d_z = 1.37, large effect size), further highlighting a more pronounced lateral asymmetry during high-speed endurance tasks. Repeated-measures analysis of variance (ANOVA) confirmed a significant main effect of velocity on total work [F(1.45, 21.75) = 28.74, P < 0.001, η² = 0.66]. Bonferroni-adjusted post-hoc comparisons revealed that total work at both 120°/s and 180°/s was significantly lower than at 60°/s (P 0.05). In summary, as angular velocity increases, trunk rotational muscle endurance exhibits a clear dominant-side (left rotation) advantage. This asymmetry becomes particularly evident in the moderate-to-high velocity range (120°/s and 180°/s), where the left rotators consistently produce significantly greater total work than the right rotators. These findings suggest that sport-specific training programs should address this bilateral imbalance to optimize core endurance and fatigue resistance in adolescent female amateur boxers. Table 2 Trunk Rotation Total Work Statistics (Unit: Joules, J) Testing Mode Angular Velocity Right Rotation Muscle Group Left Rotation Muscle Group P-value Concentric 60°/s 363.79 ± 93.56 384.67 ± 95.01 0.145 120°/s 355.36 ± 78.85 418.76 ± 74.26 0.001* 180°/s 228.12 ± 78.02 284.73 ± 98.29 0.001* Note: indicates statistical significance at P < 0.01. Values are presented as mean ± standard deviation. 3.2 Analysis of Knee Joint Concentric and Eccentric Isokinetic Strength As shown in Table 3 (Descriptive Statistics for Knee Flexor and Extensor Peak Torque), knee joint muscle peak torque (PT) under concentric (CON) and eccentric (ECC) modes exhibited clear differences related to contraction type and pronounced velocity dependence. Concentric contraction (CON) results Repeated-measures ANOVA revealed a significant main effect of velocity [F(1.38, 20.70) = 45.67, P < 0.001, η² = 0.75], indicating that PT decreased significantly with increasing angular velocity. Bonferroni post-hoc comparisons confirmed that PT at 60°/s was significantly higher than at both 120°/s and 180°/s (P < 0.01), while the difference between 120°/s and 180°/s approached significance (P = 0.08). At the slow velocity of 60°/s, extensor PT reached its highest values bilaterally (right knee: 143.78 ± 20.91 N·m; left knee: 141.87 ± 22.40 N·m), with flexor PT being considerably lower (right knee: 83.39 ± 15.72 N·m; left knee: 85.39 ± 10.76 N·m). No significant bilateral differences were observed at this velocity (paired t-tests, all P > 0.05). As velocity increased to 120°/s, right-side flexor and extensor PT became significantly higher than the left side [flexors: t( 15 ) = 2.31, P = 0.032, Cohen’s d_z = 0.58; extensors: t( 15 ) = 2.14, P = 0.044, Cohen’s d_z = 0.54], suggesting the emergence of a right-side advantage at moderate velocities. At the highest velocity of 180°/s, PT values further declined and bilateral differences disappeared (all P > 0.05). Eccentric contraction (ECC) results: Repeated-measures ANOVA showed a significant main effect of velocity [F(1.62, 24.30) = 12.89, P < 0.001, partial η² = 0.46; Greenhouse-Geisser correction applied], indicating overall differences in ECC PT across velocities. Bonferroni post-hoc tests revealed the largest difference between 60°/s and 120°/s (P 0.05). Eccentric strength was significantly greater than concentric strength across conditions (paired t-tests, overall P < 0.01), consistent with the well-established physiological principle that eccentric muscle actions produce higher force output than concentric actions. In eccentric flexion actions (quadriceps resisting machine-driven knee flexion), right-side quadriceps PT was significantly higher than the left side at all three velocities: 60°/s: 177.27 ± 47.82 N·m vs. 162.30 ± 41.23 N·m [t( 15 ) = 4.12, P = 0.001, d_z = 1.03],120°/s: 204.15 ± 56.82 N·m vs. 190.09 ± 62.94 N·m [t( 15 ) = 3.89, P = 0.001, d_z = 0.97],180°/s: 189.18 ± 47.29 N·m vs. 166.79 ± 49.80 N·m [t( 15 ) = 4.56, P < 0.001, d_z = 1.14] The largest asymmetry was observed at 120°/s (maximum right-side value: 204.15 N·m). In contrast, during eccentric extension actions (hamstrings resisting machine-driven knee extension), no significant bilateral differences were detected (all P > 0.05). These findings indicate that the right quadriceps muscle group demonstrates a marked eccentric advantage during the braking phase, likely attributable to the repeated sport-specific loading experienced by the rear (right) leg in boxing—particularly during push-off, deceleration, and rapid recovery phases—resulting in enhanced eccentric tolerance and strength on the dominant side. Summary. Under concentric conditions, knee muscle strength is dominated by slow-velocity absolute force production, with a right-side advantage emerging at moderate velocities. In eccentric mode, the right quadriceps (ECC flexion action) exhibits a more pronounced and consistent superiority across all tested velocities. These patterns suggest that boxing-specific training imparts a selective reinforcement of eccentric control capacity in the rear leg, particularly for the quadriceps muscle group. Table 3 Descriptive Statistics for Knee Flexor and Extensor Peak Torque (PT) (Unit: N·m) Testing Mode Angular Velocity Flexion Action P-value Extension Action P-value Left Knee Right Knee Left Knee Right Knee Concentric 60°/s 85.39 ± 10.76 83.39 ± 15.72 0.400 141.87 ± 22.40 143.78 ± 20.91 0.459 120°/s 74.64 ± 7.28 78.42 ± 11.82 0.032* 121.97 ± 10.16 126.00 ± 15.34 0.044* 180°/s 71.76 ± 7.09 71.36 ± 13.03 0.842 103.30 ± 9.62 105.00 ± 14.63 0.349 Eccentric 60°/s 162.30 ± 41.23 177.27 ± 47.82 0.001* 105.09 ± 20.61 101.88 ± 20.48 0.138 120°/s 190.09 ± 62.94 204.15 ± 56.82 0.001* 109.42 ± 25.82 105.61 ± 28.04 0.067 180°/s 166.79 ± 49.80 189.18 ± 47.29 0.001* 104.00 ± 21.44 103.82 ± 25.32 0.928 Note: In concentric mode, flexion action represents active hamstring (flexor) work, and extension action represents active quadriceps (extensor) work. In eccentric mode, flexion action represents quadriceps resisting machine flexion (eccentric quadriceps),and extension action represents hamstrings resisting machine extension (eccentric hamstrings). indicates statistical significance at P < 0.01. Values are mean ± standard deviation. As presented in Table 4 (Knee Flexor and Extensor Total Work Statistics), total work (TW) of the knee muscle groups under concentric (CON) and eccentric (ECC) modes exhibited distinct differences in contraction type and clear patterns of lateral asymmetry. Concentric contraction (CON) results: Repeated-measures ANOVA revealed a significant main effect of velocity on total work [F(1.32, 19.80) = 38.56, P < 0.001, η² = 0.72], indicating a substantial decline in TW with increasing angular velocity. Bonferroni post-hoc comparisons confirmed that TW at 60°/s was significantly higher than at both 120°/s and 180°/s (P 0.05). At the slow velocity of 60°/s, total work of the left knee flexors was significantly greater than the right (549.24 ± 71.01 J vs. 498.39 ± 110.45 J; paired t-test, t( 15 ) = 3.28, P = 0.005, Cohen’s d_z = 0.82, large effect size), suggesting superior flexor endurance on the left side at low velocities. In contrast, extensor total work showed no significant bilateral difference (P = 0.336). As velocity increased to 120°/s and 180°/s, bilateral differences in both flexor and extensor total work disappeared (all P > 0.05). Eccentric contraction (ECC) results: Repeated-measures ANOVA demonstrated a significant main effect of velocity [F(1.58, 23.70) = 14.23, P < 0.001, η² = 0.49], indicating overall differences in ECC total work across velocities. Bonferroni post-hoc tests showed that TW at 120°/s was significantly higher than at both 60°/s and 180°/s (P 0.05). Total work in ECC mode was significantly greater than in CON mode across conditions (paired t-tests, overall P < 0.01), consistent with the physiological characteristic that eccentric contractions produce higher mechanical work output. In eccentric flexion actions (quadriceps resisting machine-driven knee flexion), right-side quadriceps total work was significantly higher than the left side at all three velocities: 60°/s: 889.76 ± 292.17 J vs. 839.12 ± 223.87 J [t( 15 ) = 2.35, P = 0.032, d_z = 0.59]. 120°/s: 1054.97 ± 377.22 J vs. 976.69 ± 348.69 J [t( 15 ) = 3.12, P = 0.005, d_z = 0.78]. 180°/s: 947.18 ± 313.16 J vs. 820.09 ± 299.68 J [t( 15 ) = 3.78, P = 0.001, d_z = 0.95].The largest right-side advantage occurred at 120°/s (peak value: 1054.97 J), highlighting prominent endurance superiority of the right quadriceps during eccentric braking phases. In eccentric extension actions (hamstrings resisting machine-driven knee extension), a significant bilateral difference was observed only at 60°/s, with right-side total work lower than left (t( 15 ) = − 3.45, P = 0.003, d_z = − 0.86); no significant differences were found at the higher velocities (P > 0.05). Summary. Under concentric conditions, knee muscle endurance is primarily characterized by slow-velocity absolute work capacity, with a notable left-side flexor advantage evident at low speeds. In eccentric mode, the right quadriceps muscle group (ECC flexion action) demonstrates markedly superior endurance across all tested velocities. These findings likely reflect adaptive responses to the sport-specific demands placed on the rear (right) leg in boxing, particularly during push-off, deceleration, and rapid leg recovery phases. Table 4 Knee Flexor and Extensor Total Work Statistics (Unit: Joules, J) Testing Mode Angular Velocity Flexion Action (Hamstrings CON / Quadriceps ECC) P-value Extension Action (Quadriceps CON / Hamstrings ECC) P-value Left Knee Right Knee Left Knee Right Knee Concentric 60°/s 549.24 ± 71.01 498.39 ± 110.45 0.005* 802.42 ± 108.72 772.60 ± 162.86 0.336 120°/s 501.87 ± 61.74 492.27 ± 89.38 0.483 743.66 ± 69.24 755.18 ± 113.45 0.351 180°/s 430.30 ± 45.09 394.21 ± 93.86 0.022* 624.54 ± 62.61 620.12 ± 111.20 0.784 Eccentric 60°/s 839.12 ± 223.87 889.76 ± 292.17 0.032* 589.54 ± 116.73 539.78 ± 145.88 0.003* 120°/s 976.69 ± 348.69 1054.97 ± 377.22 0.005* 574.42 ± 146.97 542.27 ± 186.14 0.147 180°/s 820.09 ± 299.68 947.18 ± 313.16 0.001* 564.06 ± 162.34 568.15 ± 183.59 0.851 3.3 Analysis of Hamstring-to-Quadriceps (H/Q) Peak Torque Ratio in Left and Right Knees As shown in Table 5 (Knee Joint Peak Torque Hamstring-to-Quadriceps Ratio Statistics), the H/Q ratio under concentric (CON) and eccentric (ECC) modes exhibited distinct differences related to contraction type and velocity dependence, with pronounced bilateral asymmetry observed specifically in ECC mode. Concentric contraction (CON) results. Repeated-measures ANOVA revealed a significant main effect of velocity on the H/Q ratio [F(1.42, 21.30) = 18.45, P < 0.001, η² = 0.55], indicating a significant increase in H/Q with increasing angular velocity. Bonferroni post-hoc comparisons confirmed that the H/Q ratio at 180°/s was significantly higher than at both 60°/s and 120°/s (P 0.05). In CON mode, no statistically significant bilateral differences in H/Q ratios were detected at any tested velocity (paired t-tests, all P > 0.05). Eccentric contraction (ECC) results. Repeated-measures ANOVA showed no significant main effect of velocity on the H/Q ratio [F(1.68, 25.20) = 2.34, P = 0.118, η² = 0.14], indicating that ECC H/Q ratios did not exhibit a clear overall trend across increasing velocities. However, significant bilateral asymmetry was consistently observed: left-side H/Q ratios were significantly higher than right-side values at all three velocities: 60°/s: 66 ± 12% vs. 59 ± 12% [t( 15 ) = 3.58, P = 0.002, Cohen’s d_z = 0.583].120°/s: 60 ± 14% vs. 52 ± 7% [t( 15 ) = 4.01, P = 0.001, Cohen’s d_z = 0.70].180°/s: 65 ± 15% vs. 55 ± 9% [t( 15 ) = 4.12, P < 0.001, Cohen’s d_z = 0.765].This asymmetry progressively increased with velocity, reaching its maximum at the highest tested speed (180°/s), where the left-side H/Q exceeded the right-side value by approximately 10 percentage points. These findings suggest relatively greater eccentric strength of the right quadriceps and/or relatively weaker eccentric capacity of the left hamstrings under high-velocity conditions. The observed pattern reflects the asymmetric impact of boxing-specific training on knee muscle group balance. In adolescent amateur female athletes during a developmental stage, such eccentric bilateral imbalances may further amplify the risk of knee joint injuries, particularly anterior cruciate ligament strain or hamstring strain. Table 5 Knee Joint Peak Torque Hamstring-to-Quadriceps (H/Q) Ratio Statistics (Unit: %) Testing Mode Angular Velocity Left Knee H/Q Right Knee H/Q P-value Concentric 60°/s 61 ± 5 58 ± 8 0.115 120°/s 61 ± 6 62 ± 8 0.464 180°/s 69 ± 5 68 ± 1 0.548 Eccentric 60°/s 66 ± 12 59 ± 12 0.002* 120°/s 60 ± 14 52 ± 7 0.001* 180°/s 65 ± 15 55 ± 9 0.001* Note: indicates statistical significance at P < 0.01 (two-tailed paired t-test). Values are presented as mean ± standard deviation. The H/Q ratio is calculated as (hamstring peak torque / quadriceps peak torque) × 100%. 4. Discussion 4.1 Trunk rotational strength and bilateral asymmetry The present study revealed that in adolescent amateur female boxing athletes, concentric trunk axial rotation exhibited significant lateral asymmetry at moderate-to-high velocities: peak torque (PT) and total work (TW) of the left rotation (dominant side) were significantly greater than those of the right rotation at both 120°/s and 180°/s (P 0.05) but progressively amplified with increasing angular velocity, suggesting that lateral differences are more functionally relevant during explosive power production (120°/s) and high-velocity endurance tasks (180°/s). This velocity-dependent pattern may reflect preferential recruitment of fast-twitch muscle fibers during higher-speed rotations, as well as stronger neuromuscular adaptations on the dominant side resulting from prolonged sport-specific training stimuli ( 17 ). Trunk axial rotation constitutes a central component of the boxing punching kinetic chain, contributing 37–42% to overall punch force generation ( 2 ). The observed left-rotation dominance is primarily attributable to the repetitive execution of rear-hand straight punches and hooks in the orthodox stance: forceful left rotation is driven predominantly by synergistic contraction of the left internal oblique, ipsilateral latissimus dorsi, and right external oblique muscles, whereas right rotation is more frequently utilized in defensive maneuvers, feints, or preparatory actions. This unilateral loading pattern aligns with asymmetry trends commonly reported in combat sports. Recent cross-disciplinary investigations in mixed martial arts (MMA) athletes have demonstrated strong correlations between trunk rotational strength and shoulder internal/external rotation, with asymmetries becoming particularly pronounced during alternating offensive-defensive sequences ( 17 ). In contrast, while unilateral-dominant sports such as tennis and golf also exhibit marked rotational asymmetries ( 18 ), the relative peak torque normalized to body weight observed in the present cohort at 120°/s (1.68–1.87 N·m·kg⁻¹) is lower than values typically reported in trunk-dominant combat disciplines such as judo and wrestling (> 2.0 N·m·kg⁻¹). This difference underscores that punching performance in boxing relies more heavily on coordinated upper-limb kinetics and rapid torque transfer rather than maximal absolute rotational strength. The asymmetry observed here is likely a direct consequence of the long-term unilateral emphasis inherent in boxing training. The dominant (left-rotating) side is repeatedly trained for powerful, accurate, and aggressive punching, whereas the non-dominant (right-rotating) side is primarily engaged in probing, rapid directional changes, and defensive actions, resulting in substantial strength imbalance in the axial rotators. Under modern scoring systems that reward higher punch volume and frequent offensive-defensive transitions, this imbalance may be further exacerbated, as the dominant side bears a disproportionately higher cumulative load ( 19 ). Existing evidence indicates that rotational asymmetry can compromise dynamic spinal stability and is closely associated with lower back pain and lumbar injuries( 20 ). Although the cross-sectional design of the current study precludes causal inference, the combination of dominant-side overload and potential fatigue-induced declines in neuromuscular control—such as reduced central drive and impaired proprioceptive input—may elevate the risk of cumulative injury to the lumbar paraspinal muscles, latissimus dorsi, and associated structures, particularly during high-intensity sparring or competition scenarios involving rapid evasive maneuvers, hurried rotations, or missed punches. Prospective longitudinal studies are warranted to establish causality and track the temporal progression of these asymmetries. To mitigate this risk, future training interventions should prioritize bilateral symmetry development, with particular emphasis on strengthening right-sided anti-rotation and anti-lateral flexion exercises. Such targeted training may enhance spinal stability, improve core endurance under asymmetric loading, and reduce the long-term likelihood of lumbar injury in adolescent female amateur boxers. 4.2 Concentric Knee Strength Characteristics The concentric (CON) testing results of the present study demonstrated that peak torque (PT) and total work (TW) of the knee extensor muscle group were significantly greater than those of the flexor group (P < 0.01). All measured parameters reached their maximum values at the slowest angular velocity of 60°/s and declined markedly as velocity increased to 120°/s and 180°/s. This velocity-dependent reduction is consistent with the classic force-velocity relationship (Hill curve), wherein slow-velocity contractions primarily reflect maximal absolute strength (predominantly slow-twitch fiber recruitment and maximal neural drive), whereas higher velocities emphasize explosive power and muscular endurance (fast-twitch fiber recruitment with rapid fatigue and limited neural drive). This pattern has been extensively documented in lower-limb isokinetic assessments and represents a key characteristic for evaluating sport-specific strength profiles in athletes ( 21 , 22 ). In bilateral comparisons, extensor PT at 60°/s was slightly higher on the right side than the left (143.78 ± 20.91 N·m vs. 141.87 ± 22.40 N·m), although the difference did not reach statistical significance (P > 0.05). However, at the moderate velocity of 120°/s, both flexor and extensor PT were significantly greater on the right side compared to the left (P < 0.05–0.01, Cohen’s d_z ≈ 0.40–0.55, medium effect sizes). This finding indicates a more pronounced right-side (rear-leg) advantage during moderate-velocity explosive force production. The observation aligns closely with the biomechanics of boxing in the orthodox stance: the rear (right) leg serves as the primary driver of ground reaction force and initiates momentum transfer for rear-hand straight punches and hooks. Prolonged repetitive training likely induces adaptive strength enhancements in the right quadriceps and hamstrings, resulting in sport-specific unilateral asymmetry( 14 ) ( 9 ). Quantitative comparisons revealed that the concentric knee flexor PT (83.39–85.39 N·m) and extensor PT (141.87–143.78 N·m) at 60°/s in the present cohort of adolescent amateur female boxers were substantially lower than values reported for female basketball players at comparable velocities [flexors: 115 ± 21.03–120.41 ± 19.50 N·m; extensors: 188.82 ± 59.37–196.82 ± 46.70 N·m], as well as recent data from amateur boxers [14]. Nevertheless, the values were higher than those typically observed in age-matched non-athletic female adolescents (quadriceps ≈ 100 N·m; hamstrings ≈ 55 N·m) [23]. These findings suggest that lower-limb absolute strength in amateur female boxers remains relatively modest, possibly due to training programs that prioritize technical-tactical repetition and sport-specific skill execution over high-intensity lower-body resistance training (particularly heavy squats, explosive leg drives, and eccentric loading). Compared with elite-level boxing or lower-limb dominant sports such as basketball, this relative strength deficit may limit the efficiency of kinetic chain momentum transfer during punching and increase the risk of compromised knee joint stability. To address this gap, it is recommended to incorporate dedicated lower-limb strength modules into training programs: ( 1 ) Implement moderate-to-high velocity (120–180°/s) isokinetic or isotonic squat and single-leg drive exercises to enhance right-side explosive power output; ( 2 ) Prioritize strengthening of the non-dominant (left) side to prevent further amplification of existing asymmetry; ( 3 ) Integrate plyometric training (e.g., box jumps, depth jumps) to specifically target velocity-dependent force production. Such targeted interventions are expected to optimize kinetic chain efficiency, improve punch force transmission, and reduce the potential for knee-related injury risk in this population. 4.3 Eccentric Knee Strength and Bilateral Differences In eccentric (ECC) mode, knee joint muscle strength was significantly greater than in concentric (CON) mode (P < 0.01), consistent with well-established physiological principles: eccentric contractions typically produce 1.2–1.8 times greater force than concentric contractions. This enhanced force capacity arises primarily from stretch-reflex activation (increased muscle spindle sensitivity), passive elastic energy storage within the muscle-tendon unit (MTU), and preferential recruitment of type II fast-twitch fibers ( 23 ). In boxing, this eccentric advantage is particularly critical, as defensive maneuvers, rapid directional changes, and landing impact absorption all rely on eccentric knee control to dissipate ground reaction forces, maintain postural stability, and prevent knee hyperextension or anterior cruciate ligament (ACL) injury. The present findings demonstrated that, during ECC testing, right-side flexor group performance (hamstrings resisting machine-driven knee extension) exhibited significantly higher peak torque (PT) and total work (TW) compared to the left side (P < 0.01, Cohen’s d_z ≈ 0.23–0.46, small to medium effect sizes). This right-side superiority was most pronounced at the moderate velocity of 120°/s, where right quadriceps eccentric PT (resisting machine-driven knee flexion) reached 204.15 ± 56.82 N·m. This pattern likely reflects sport-specific neuromuscular adaptations in orthodox-stance boxers: the rear (right) leg must exert powerful eccentric control following rear-hand punch delivery to stabilize the base of support, rapidly retract the center of mass, and absorb landing impact forces. Repeated exposure to these demands over time appears to selectively enhance eccentric tolerance and strength in the right hamstrings and quadriceps, resulting in a boxing-specific unilateral asymmetry( 14 ). Compared with CON mode, the substantially greater force output and work capacity in ECC mode (with TW peaking at 1054.97 ± 377.22 J at 120°/s) underscore the potential efficacy of eccentric training for improving overall muscle strength and agonist-antagonist balance. Recent meta-analyses have shown that 4–12 weeks of structured eccentric training can significantly increase knee joint PT and H/Q ratios (with improvements ranging from 10–20%) and reduce the risk of hamstring strain injuries ( 24 , 25 ). Nonetheless, the dual-edged nature of eccentric loading must be carefully considered ( 26 ): high-intensity eccentric contractions are known to induce delayed-onset muscle soreness (DOMS) and microscopic muscle damage (Z-line disruption, inflammatory responses) ( 27 , 28 ). In the presence of pre-existing right-side dominance, unmonitored eccentric loading could further exacerbate bilateral asymmetry and elevate the cumulative risk of overuse injury ( 29 ). Therefore, eccentric training protocols should incorporate strict intensity control (initially 70–80% of 1RM), progressive overload, and comprehensive recovery strategies—including foam rolling, static stretching, and nutritional support—to minimize adverse effects. Overall, while the right-side flexor dominance observed in ECC mode optimizes rear-leg braking and support function during punching sequences, it also highlights the need for targeted eccentric strengthening of the non-dominant (left) side. Such balanced eccentric training is recommended to restore bilateral symmetry, enhance knee joint stability, and reduce the long-term risk of knee-related injuries in adolescent amateur female boxers. 4.4 Hamstring-to-Quadriceps (H/Q) Ratios The present study demonstrated that in concentric (CON) mode, the hamstring-to-quadriceps peak torque ratio (H/Q ratio) progressively increased with angular velocity across 60°/s, 120°/s, and 180°/s, with no statistically significant bilateral differences at any velocity (all P > 0.05). This velocity-dependent increase aligns with well-established isokinetic testing patterns: quadriceps (extensor) strength declines more rapidly at higher velocities compared to the hamstrings (flexors), resulting in an elevated H/Q ratio ( 30 ) ( 31 ) ( 32 ). In contrast, eccentric (ECC) mode revealed pronounced bilateral asymmetry, with left-side H/Q ratios significantly higher than right-side values at all tested velocities: 60°/s: 66 ± 12% vs. 59 ± 12% (P = 0.002, Cohen’s d_z = 0.583, medium effect size) ,120°/s: 60 ± 14% vs. 52 ± 7% (P = 0.001, Cohen’s d_z = 0.70, medium-to-large effect size),180°/s: 65 ± 15% vs. 55 ± 9% (P < 0.001, Cohen’s d_z = 0.765, large effect size) The asymmetry intensified with increasing velocity, reaching its maximum at 180°/s. The H/Q ratio, defined as hamstring peak torque divided by quadriceps peak torque (expressed as a percentage), typically ranges from 30% to 90% in healthy populations and plays a critical role in maintaining knee joint stability ( 33 ). An inadequate agonist-antagonist balance can compromise dynamic knee control and increase the risk of ligamentous and muscular injuries. Conventional consensus holds that a low concentric H/Q ratio at 60°/s is strongly associated with anterior cruciate ligament (ACL) injury and hamstring strain risk ( 34 ). In the current cohort, the CON H/Q ratios at 60°/s fell below or at the lower end of the critical threshold, and were modestly lower than normative values reported for elite female athletes in other sports (e.g., 48–70% in elite female basketball and volleyball players, with higher values in basketball groups ( 35 )). These findings suggest relative hamstring weakness compared to quadriceps strength in adolescent amateur female boxers, likely reflecting an overemphasis on quadriceps-dominant push-off actions during punching sequences, while hamstring reinforcement has received insufficient attention in training programs. The marked lateral asymmetry in ECC mode further exacerbates this imbalance: a higher left-side H/Q indicates relatively stronger eccentric hamstring performance on the left and/or greater eccentric quadriceps dominance on the right. This pattern is consistent with boxing-specific demands in the orthodox stance, where the rear (right) leg experiences substantial eccentric loading to absorb ground reaction forces, decelerate forward momentum, and rapidly retract the center of mass following rear-hand punch delivery. Prolonged exposure to these asymmetric demands appears to preferentially enhance eccentric quadriceps capacity on the dominant side, while hamstring eccentric strength lags behind. Recent investigations in female competitive athletes have similarly linked abnormal H/Q ratios—particularly low functional eccentric/concentric ratios—to elevated knee injury risk, with asymmetry amplifying the likelihood of ACL rupture or chronic hamstring strain in unilaterally dominant sports [15, 36] ( 15 , 35 ). From a physiological perspective, deviations in the H/Q ratio often reflect impaired neuromuscular coordination: excessive quadriceps dominance may inhibit co-activation of the hamstrings, thereby reducing dynamic knee stability ( 36 , 37 ). During adolescence, such imbalances warrant particular caution, as hormonal fluctuations, delayed neuromuscular maturation, and training-induced biases can further magnify asymmetry ( 38 ). To prevent potential knee joint injuries and optimize muscle group balance, the following targeted interventions are recommended: ( 1 ) Prioritize eccentric hamstring strengthening exercises (e.g., Nordic hamstring curls, isokinetic eccentric training at 60–120°/s; structured 4–8-week protocols can increase H/Q ratios by 10–15%); ( 2 ) Incorporate functional neuromuscular training (e.g., single-leg landing deceleration tasks, agility ladder drills) to enhance agonist-antagonist coordination; ( 3 ) Implement regular isokinetic monitoring of H/Q ratios—particularly in ECC mode—to detect and correct emerging bilateral discrepancies and guide individualized training adjustments. These strategies are expected not only to maintain H/Q ratios within a safer range (> 0.60–0.65) but also to improve knee joint stability during rapid directional changes and braking maneuvers, thereby supporting long-term health and athletic performance in adolescent female amateur boxers. 4.5 Integrated Implications for the Boxing Kinetic Chain and Injury Prevention Punching in boxing constitutes a sequential closed kinetic chain action involving the foot-ankle-knee-hip-trunk-upper limb segments ( 39 ). Ground reaction forces are generated through lower-limb drive, transmitted via knee extension and eccentric control to the hip, and subsequently amplified through trunk axial rotation—particularly leftward rotation during dominant rear-hand punches—before being efficiently converted into upper-limb impact force. The present findings demonstrate a highly synergistic pattern between left-dominant trunk rotation and right-side eccentric knee flexor superiority (right significantly greater than left, P < 0.01). Left trunk rotation provides the primary rotational torque, while right knee extension and eccentric braking ensure stable rear-leg support and rapid center-of-mass recovery, collectively forming an efficient force transmission pathway. This “dominant-side reinforcement” configuration is consistent with the biomechanical demands of orthodox-stance boxing, where rear-hand straight punches and hooks rely predominantly on right-leg push-off combined with leftward trunk rotation. However, this specialized adaptation introduces substantial overload risk to the dominant side (left trunk rotators + right knee). Prolonged high-magnitude loading on these segments may predispose athletes to cumulative injury of the lumbar paraspinal muscles and latissimus dorsi, as well as increased susceptibility to anterior cruciate ligament (ACL) strain or hamstring injury at the knee. This observation aligns with kinetic chain compensation theory: functional deficits or imbalances in one segment amplify mechanical stress on proximal and distal links ( 40 ) ( 22 ). Fatigue further exacerbates these asymmetry-related risks. Under conditions of reduced central neural drive, diminished muscle spindle sensitivity, and compromised proprioceptive input, trunk rotational excursion may increase uncontrollably, while eccentric knee braking capacity declines. Such neuromuscular impairment is particularly pronounced during competitive bouts or high-intensity training sessions involving rapid evasive maneuvers, hurried rotations, or missed punches, potentially leading to excessive joint loading and loss of dynamic stability ( 41 ). Compared with elite-level boxers, the adolescent amateur female cohort in this study exhibited lower absolute lower-limb strength and more pronounced asymmetry (larger effect sizes), likely reflecting developmental-stage training programs that overemphasize technical-tactical repetition while under-prioritizing balanced strength development. This imbalance may further heighten the long-term risk of knee joint and lumbar injuries. Overall, while the observed kinetic chain synergy optimizes punching efficiency, the combination of dominant-side overload and non-dominant-side weakness creates a vulnerability that can evolve into an injury “perfect storm” under fatigue or high-intensity conditions. To mitigate these risks and enhance long-term athletic health, the following integrated training strategies are recommended: ( 1 ) Implement bilateral trunk rotational balance training, with particular emphasis on right-side anti-rotation and anti-lateral flexion exercises (e.g., medicine ball rotational throws, cable wood chops, or Pallof presses). ( 2 ) Strengthen non-dominant (left) knee eccentric capacity through targeted eccentric protocols (e.g., isokinetic eccentric training at 60–120°/s or eccentric single-leg squats). ( 3 ) Monitor and maintain hamstring-to-quadriceps (H/Q) ratios above 0.60–0.65, prioritizing eccentric hamstring reinforcement (e.g., Nordic hamstring curls, glute-ham raises, or eccentric isokinetic hamstring exercises). ( 4 ) Conduct periodic isokinetic assessments to track asymmetry progression, integrate fatigue management strategies (e.g., avoiding consecutive high-load eccentric sessions), and incorporate adequate recovery periods. These interventions are expected not only to reduce the likelihood of lumbar and knee injuries but also to further enhance kinetic chain efficiency and punching performance. Future prospective longitudinal studies are needed to validate the long-term efficacy of these balanced training approaches in adolescent female amateur boxers. 5. Conclusions and Practical Applications The present study demonstrates that adolescent amateur female boxing athletes exhibit significant asymmetries in trunk axial rotation (left > right) and knee joint eccentric strength (right flexors > left), accompanied by relatively low absolute lower-limb strength compared with athletes in similar combat sports. The pronounced bilateral differences in eccentric hamstring-to-quadriceps (H/Q) ratios further highlight an imbalance that may elevate the risk of overuse injuries to the dominant-side lumbar region and knee joint structures. These findings reflect sport-specific neuromuscular adaptations driven by the repetitive unilateral demands of orthodox-stance punching mechanics—particularly rear-hand power generation involving right-leg drive and leftward trunk rotation—while revealing potential vulnerabilities resulting from inadequate bilateral balance and insufficient emphasis on eccentric control and hamstring reinforcement during developmental training phases. Practical Applications To mitigate injury risk, enhance kinetic chain efficiency, and optimize long-term athletic performance, the following evidence-based training recommendations are proposed: ( 1 ) Balance trunk rotational strength Incorporate targeted exercises to strengthen the non-dominant (right) rotators and improve anti-rotation/anti-lateral flexion capacity. Examples include medicine ball rotational throws, cable woodchoppers, Pallof presses, and landmine anti-rotation presses. Perform 2–3 sessions per week, integrated with core stability drills (e.g., planks with perturbations, bird dogs), to reduce asymmetric lumbar loading and enhance spinal dynamic stability. ( 2 ) Strengthen non-dominant (left) knee rapid force production Prioritize eccentric and concentric training of the left knee extensors and flexors to improve front-leg support function and coordination with rear-leg drive. Utilize isokinetic eccentric/concentric protocols (60–180°/s) and plyometric exercises (e.g., single-leg box drops, lateral bounds, depth jumps with controlled landing). This targeted approach aims to reduce bilateral asymmetry, enhance overall lower-limb symmetry, and support more efficient force transmission during punching sequences. ( 3 ) Optimize hamstring-to-quadriceps (H/Q) ratio Implement structured eccentric hamstring strengthening to elevate and maintain the H/Q ratio above 0.60–0.65, particularly in eccentric mode. Key exercises include Nordic hamstring curls (progressive volume and load), glute-ham raises, and isokinetic eccentric hamstring training at 60–120°/s. A 4–8-week progressive program has been shown to yield meaningful improvements in H/Q ratios and reduce hamstring strain risk, while concurrently supporting anterior cruciate ligament protection. ( 4 ) Regular isokinetic monitoring and fatigue management Conduct periodic isokinetic assessments (every 8–12 weeks) to track changes in bilateral asymmetry, velocity-dependent strength profiles, and H/Q ratios. Combine this surveillance with deliberate fatigue management strategies, such as avoiding consecutive high-intensity eccentric sessions, incorporating adequate recovery periods (48–72 hours between heavy lower-limb sessions), and monitoring subjective fatigue markers. These measures will help minimize cumulative overload, prevent exacerbation of existing asymmetries, and sustain improvements in punching efficiency and injury resilience. Implementation of these practical recommendations—emphasizing bilateral symmetry, eccentric control, and ongoing monitoring—offers a proactive framework to safeguard musculoskeletal health while simultaneously enhancing sport-specific performance in adolescent amateur female boxers. Longitudinal follow-up studies are encouraged to evaluate the long-term efficacy of these integrated interventions on injury incidence and competitive outcomes. Declarations Ethics approval and consent to participate This study was approved by the Ethics Committee of Shanghai University of Sport (approval number: 102772019RT033). The study was conducted in accordance with the Declaration of Helsinki. All participants provided written informed consent prior to their participation in the study. Consent for publication All authors have approved this manuscript for publication. This manuscript has not previously been published and is not pending publication elsewhere. Competing interests The authors declare no competing interests. Data availability statement The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request. Author Contributions Yang Liu and Zhiyong Chen Writing– original draft, Writing – review & editing. Jian Xiao: Conceptualization, Methodology, Funding acquisition, Project administration .All authors have read and agreed to the published version of the manuscript. Funding This study was supported by the National-sponsored Social Sciences Funding Program (23BTY051). References Liu YZ, Chen ZQ, Deng XX, Ma CY, Zhao XJ. Biomechanics of the lead straight punch of different level boxers. Front Physiol. 2022;13:1–9. https://doi:10.3389/fphys.2022.1015154 . Filimonov VI, Koptsev KN, Husyanov ZM et al. Boxing: Means of increasing strength of the punch. Natl Strength Conditioning Association J. 1985;7(6). Hislop HJ, Perrine JJ. The isokinetic concept of exercise. Phys Ther. 1967;47(2):114. van der Woude DR, Ruyten T, Bartels B. Reliability of Muscle Strength and Muscle Power Assessments Using Isokinetic Dynamometry in Neuromuscular Diseases: A Systematic Review. Phys Ther. 2022;102(10). https://doi:10.1093/ptj/pzac099 . Guérin M, Sijobert B, Zaragoza B, Cambon F, Boyer L, Patte K. Combining Intensive Rehabilitation With a Nonfunctional Isokinetic Strengthening Program in Adolescents With Cerebral Palsy: Protocol for a Randomized Controlled Trial. JMIR Res protocols. 2023;12:e43221. https://doi:10.2196/43221 . Ayala F, De Ste Croix M, Sainz de Baranda P, Santonja F. Absolute reliability of isokinetic knee flexion and extension measurements adopting a prone position. Clin Physiol Funct Imaging. 2013;33(1):45–54. https://doi:10.1111/j.1475-097X.2012.01162.x . Huang H, Guo J, Yang J, Jiang Y, Yu Y, Müller S, et al. Isokinetic angle-specific moments and ratios characterizing hamstring and quadriceps strength in anterior cruciate ligament deficient knees. Sci Rep. 2017;7(1):7269. https://doi:10.1038/s41598-017-06601-5 . Kocahan T, Akınoğlu B. Determination of the relationship between core endurance and isokinetic muscle strength of elite athletes. J Exerc rehabilitation. 2018;14(3):413–8. https://doi:10.12965/jer.1836148.074 . Chen C, Ali Z, Rashid MAR, Samethanovna MU, Wu GD, Mukhametkali S, et al. Relationship between isokinetic strength of the knee joint and countermovement jump performance in elite boxers. PeerJ. 2023;11:1–14. https://doi:10.7717/peerj.16521 . Brukner P, Nealon A, Morgan C, Burgess D, Dunn A. Recurrent hamstring muscle injury: applying the limited evidence in the professional football setting with a seven-point programme. Br J Sports Med. 2014;48(11):929–38. https://doi:10.1136/bjsports-2012-091400 . Tasiopoulos I, Nikolaidis PT, Tripolitsioti A, Stergioulas A, Rosemann T, Knechtle B. Isokinetic Characteristics of Amateur Boxer Athletes. Front Physiol. 2018;9:1597. https://doi:10.3389/fphys.2018.01597 . Tunstall H, Mullineaux DR, Vernon T. Criterion validity of an isokinetic dynamometer to assess shoulder function in tennis players. Sports Biomech. 2005;4(1):101–11. https://doi:10.1080/14763140508522855 . Liu YL, Jiang L, Geng M. Comparative effects of unilateral, bilateral, and hybrid combined resistance training on straight punch performance in adolescent boxers: a focus on dominant and non-dominant-side adaptations. Eur J Appl Physiol. 2025. https://doi:10.1007/s00421-025-05913-z . Zhou ZX, Chen C, Chen X, Yi WJ, Cui WJ, Wu R, et al. Lower extremity isokinetic strength characteristics of amateur boxers. Front Physiol. 2022;13. https://doi:10.3389/fphys.2022.898126 . Myer GD, Sugimoto D, Thomas S, Hewett TE. The influence of age on the effectiveness of neuromuscular training to reduce anterior cruciate ligament injury in female athletes: a meta-analysis. Am J Sports Med. 2013;41(1):203–15. https://doi:10.1177/0363546512460637 . Faul F, Erdfelder E, Lang A-G, Buchner A. G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007;39(2):175–91. https://doi:10.3758/BF03193146 . Hank M, Miratsky P, Ford KR, Clarup C, Imal O, Verbruggen FF, et al. Exploring the interplay of trunk and shoulder rotation strength: a cross-sport analysis. Front Physiol. 2024;15:1371134. https://doi:10.3389/fphys.2024.1371134 . Ellenbecker TS, Roetert EP. An isokinetic profile of trunk rotation strength in elite tennis players. Med Sci Sports Exerc. 2004;36(11):1959–63. https://doi:10.1249/01.mss.0000145469.08559.0e . Davis P, Benson PR, Pitty JD, Connorton AJ, Waldock R. The Activity Profile of Elite Male Amateur Boxing. Int J Sport Physiol Perform. 2015;10(1):53–7. 10.1123/ijspp.2013-0474 . https://doi . Kumar S, Dufresne RM, Van Schoor T. Human trunk strength profile in lateral flexion and axial rotation. Spine. 1995;20(2):169–77. https://doi:10.1097/00007632-199501150-00007 . Drouin JM, Valovich-mcLeod TC, Shultz SJ, Gansneder BM, Perrin DH. Reliability and validity of the Biodex system 3 pro isokinetic dynamometer velocity, torque and position measurements. Eur J Appl Physiol. 2004;91(1):22–9. https://doi:10.1007/s00421-003-0933-0 . Dong K, Yu T, Chun B. Effects of Core Training on Sport-Specific Performance of Athletes: A Meta-Analysis of Randomized Controlled Trials. Behavioral sciences (Basel, Switzerland). 2023;13(2). https://doi:10.3390/bs13020148 Herzog W. Why are muscles strong, and why do they require little energy in eccentric action? J Sport Health Sci. 2018;7(3):255–64. https://doi:10.1016/j.jshs.2018.05.005 . Yagiz G, Akaras E, Kubis HP, Owen JA. Heterogeneous effects of eccentric training and nordic hamstring exercise on the biceps femoris fascicle length based on ultrasound assessment and extrapolation methods: A systematic review of randomised controlled trials with meta-analyses. PLoS ONE. 2021;16(11):e0259821. https://doi:10.1371/journal.pone.0259821 . Androulakis Korakakis P, Wolf M, Coleman M, Burke R, Piñero A, Nippard J, et al. Optimizing Resistance Training Technique to Maximize Muscle Hypertrophy: A Narrative Review. J Funct morphology Kinesiol. 2023;9(1). https://doi:10.3390/jfmk9010009 . Stauber WT. Eccentric action of muscles: physiology, injury, and adaptation. Exerc Sport Sci Rev. 1989;17:157–85. Shalmon G, Shapira G, Ibrahim R, Israel-Elgali I, Grad M, Shlayem R, et al. Maximal and sub-maximal exercise tests alter PBMC microRNA expression: insights into sport- and sex-specific variations. Front Physiol. 2025;16:1583870. https://doi:10.3389/fphys.2025.1583870 . Meng Q, Su CH. The Impact of Physical Exercise on Oxidative and Nitrosative Stress: Balancing the Benefits and Risks. Antioxid (Basel Switzerland). 2024;13(5). https://doi:10.3390/antiox13050573 . Arvanitidis M, Jiménez-Grande D, Haouidji-Javaux N, Falla D, Martinez-Valdes E. Eccentric exercise-induced delayed onset trunk muscle soreness alters high-density surface EMG-torque relationships and lumbar kinematics. Sci Rep. 2024;14(1):18589. https://doi:10.1038/s41598-024-69050-x . Aagaard P, Simonsen EB, Andersen JL, Magnusson SP, Bojsen-Møller F, Dyhre-Poulsen P. Antagonist muscle coactivation during isokinetic knee extension. Scand J Med Sci Sports. 2000;10(2):58–67. https://doi:10.1034/j.1600-0838.2000.010002058.x . Coombs R, Garbutt G. Developments in the use of the hamstring/quadriceps ratio for the assessment of muscle balance. J sports Sci Med. 2002;1(3):56–62. Remaud A, Cornu C, Guével A. Agonist muscle activity and antagonist muscle co-activity levels during standardized isotonic and isokinetic knee extensions. J Electromyogr kinesiology: official J Int Soc Electrophysiological Kinesiol. 2009;19(3):449–58. 10.1016/j.jelekin.2007.11.001 . https://doi . Nosse LJ. Assessment of selected reports on the strength relationship of the knee musculature*. J Orthop Sports Phys Ther. 1982;4(2):1. Ruas CV, Pinto RS, Haff GG, Lima CD, Pinto MD, Brown LE. Alternative Methods of Determining Hamstrings-to-Quadriceps Ratios: a Comprehensive Review. Sports Med Open. 2019;5(1):11. https://doi:10.1186/s40798-019-0185-0 . Kabacinski J, Murawa M, Mackala K, Dworak LB. Knee strength ratios in competitive female athletes. PLoS ONE. 2018;13(1):e0191077. https://doi:10.1371/journal.pone.0191077 . Krosshaug T, Nakamae A, Boden BP, Engebretsen L, Smith G, Slauterbeck JR, et al. Mechanisms of anterior cruciate ligament injury in basketball: video analysis of 39 cases. Am J Sports Med. 2007;35(3):359–67. https://doi:10.1177/0363546506293899 . Tosarelli F, Buckthorpe M, Di Paolo S, Grassi A, Rodas G, Zaffagnini S, et al. Video Analysis of Anterior Cruciate Ligament Injuries in Male Professional Basketball Players: Injury Mechanisms, Situational Patterns, and Biomechanics. Orthop J sports Med. 2024;12(3):23259671241234880. https://doi:10.1177/23259671241234880 . Hewett TE, Myer GD, Ford KR, Paterno MV, Quatman CE. Mechanisms, prediction, and prevention of ACL injuries: Cut risk with three sharpened and validated tools. J Orthop research: official publication Orthop Res Soc. 2016;34(11):1843–55. https://doi:10.1002/jor.23414 . Xu X, Sun Y, Zhu D. Analysis of the impact force and key technique of backward straight punch in different combat sports. Sci Rep. 2025;15(1):10958. https://doi:10.1038/s41598-025-96264-4 . Saeterbakken AH, Sandvikmoen TE, Iversen E, Bjørnsen T, Stien N, Andersen V, et al. The effect of heavy-resistance core strength training on upper-body strength and power performance in national-level junior athletes-a pilot study. Front Physiol. 2025;16:1617104. https://doi:10.3389/fphys.2025.1617104 . Sašek M, Šarabon N, Smajla D. Exploring the relationship between lower limb strength, strength asymmetries, and curvilinear sprint performance: Findings from a pilot study. Sci Prog. 2024;107(2):368504241247998. https://doi:10.1177/00368504241247998 . Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 29 Apr, 2026 Reviewers agreed at journal 20 Apr, 2026 Reviews received at journal 26 Mar, 2026 Reviewers agreed at journal 26 Mar, 2026 Reviewers agreed at journal 20 Mar, 2026 Reviewers invited by journal 18 Mar, 2026 Editor invited by journal 16 Mar, 2026 Editor assigned by journal 16 Mar, 2026 Submission checks completed at journal 16 Mar, 2026 First submitted to journal 14 Mar, 2026 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-9121035","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":609784865,"identity":"302df6f0-1ec7-4197-b15f-25ea67768a8d","order_by":0,"name":"Yang Liu","email":"","orcid":"","institution":"Nanjing Sport Institute","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Liu","suffix":""},{"id":609784866,"identity":"83c9d2da-c736-4a27-97d5-3bf2089bce24","order_by":1,"name":"Jian Xiao","email":"","orcid":"","institution":"Nanchang Normal University","correspondingAuthor":false,"prefix":"","firstName":"Jian","middleName":"","lastName":"Xiao","suffix":""},{"id":609784867,"identity":"702ede19-8513-4a6c-af4d-bf089401d8aa","order_by":2,"name":"Zhiyong Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxElEQVRIie3QMQrCQBCF4QmB2IymXSGFRxgQUi3kIDYjwna2kiJFQEhKD+BlDAOmCdraublBSkvTWkjWzmK/ev7iDYDn/aHs2bYD5xrjMBTr1jzQgO1MsqwjQ44JpEFfiaY7rpRTEZxLY7eVwbUgEBR6M5mESdMS3zSmMr9YuJp9OZVEwKz4YMZkwRSUMp0gMCmOBNdHJOWUKMWp4kqQQteEsNsRdwaVjE9mly00q5v+lessPonYodDTySf+7dzzPM/75g3vWj+3YCONFwAAAABJRU5ErkJggg==","orcid":"","institution":"Tongji Zhejiang College","correspondingAuthor":true,"prefix":"","firstName":"Zhiyong","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2026-03-14 08:53:40","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9121035/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9121035/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105212408,"identity":"e03037c5-f878-41df-aa82-d222fa95bc7e","added_by":"auto","created_at":"2026-03-23 13:59:41","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":47050,"visible":true,"origin":"","legend":"\u003cp\u003eG*Power output for sample size calculation (paired t-test, d_z = 0.5, α = 0.05, power = 0.95).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9121035/v1/f454e1b87ae12e16656ff9cf.png"},{"id":105563751,"identity":"4ad0f501-94ff-4199-a924-ef94e6543277","added_by":"auto","created_at":"2026-03-27 12:47:42","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":829130,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSetup for knee joint and trunk rotation isokinetic testing in female boxers.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9121035/v1/2e46ada17ce51382b51e46ff.png"},{"id":105569177,"identity":"402b3b8c-f080-44e5-9598-fca0c107f331","added_by":"auto","created_at":"2026-03-27 13:11:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1994998,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9121035/v1/ded28b97-9289-4383-82ff-0c5a1cc7298f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Isokinetic strength characteristics of trunk rotation and knee joint in female amateur boxers: asymmetry and implications for injury prevention","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePunching power in boxing primarily originates from lower limb drive, with efficient momentum transfer to the upper limbs achieved through knee joint flexion-extension and hip/trunk rotation (\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e) (\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e) Lower limb initiation, core trunk transmission efficiency, and upper-lower limb coordination are critical determinants of punch timing, force output, and overall performance. Therefore, a systematic evaluation of knee joint and trunk rotational muscle strength characteristics in boxers is of significant importance for optimizing sport-specific strength training and preventing injuries.\u003c/p\u003e\n\u003cp\u003eIsokinetic dynamometry (\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e) is widely regarded as the gold standard for assessing single-joint muscle group strength. By automatically adjusting resistance according to joint angular velocity, it enables precise measurement of peak torque (PT), total work (TW) throughout the full range of motion, while distinguishing between concentric (CON) and eccentric (ECC) contraction modes (\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e). Isokinetic devices are extensively used in athlete strength profiling, fatigue induction, and injury rehabilitation, particularly for analyzing velocity-dependent strength and muscle group balance (e.g., hamstring-to-quadriceps [H/Q] ratio) (\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eRecent isokinetic strength studies in boxers have primarily focused on the knee and shoulder rotator muscle groups (\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e). For instance, Chen et al. (\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e) reported that knee extensor strength in amateur boxers is significantly correlated with elite-level performance, and bilateral asymmetry or abnormal H/Q ratios may increase the risk of knee injuries (\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e). Tasiopoulos et al. identified associations between shoulder rotator strength asymmetry and boxing performance (\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e), yet trunk rotation was not addressed. Trunk axial rotation constitutes a key link in the boxing punching kinetic chain, contributing 37.2\u0026ndash;45.0% to punch force generation (\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e). However, isokinetic assessments of trunk rotation remain scarce and are more commonly reported in unilateral-dominant sports such as tennis and golf (\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e). Existing literature indicates that combat sport athletes frequently exhibit rotational muscle asymmetry (dominant side\u0026thinsp;\u0026gt;\u0026thinsp;non-dominant side), likely resulting from prolonged unilateral technical training, which may compromise lumbar stability and elevate injury risk (\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eNotably, research on female and adolescent boxers is scarce. Available isokinetic knee data predominantly derive from adult male or mixed-sex samples (\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e). In female amateur and adolescent populations, muscle strength characteristics during developmental stages, bilateral asymmetry, and H/Q ratios may exhibit distinct patterns that are closely linked to injury susceptibility (\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e). Moreover, no systematic studies have yet integrated concentric/eccentric knee testing with concentric trunk rotation assessments while emphasizing asymmetry analysis.\u003c/p\u003e\n\u003cp\u003eIn light of these gaps, the present study employed the IsoMed 2000 isokinetic dynamometer to evaluate knee concentric/eccentric and trunk rotation concentric strength (at 60\u0026deg;/s, 120\u0026deg;/s, and 180\u0026deg;/s) in adolescent amateur female boxers (national level 1 or 2). The investigation systematically examined bilateral strength characteristics, asymmetry patterns, and H/Q ratios, with the aim of elucidating muscle strength profiles in this population and providing evidence-based guidance for balanced sport-specific training and injury prevention.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"1 Subjects and Data Processing","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e\n\u003ch2\u003e1.1 Subjects\u003c/h2\u003e\n\u003cp\u003eSixteen female boxing athletes from the Competitive Sports School of Shanghai University of Sport (coded as boxer01 to boxer16) participated in the study. All subjects adopted an orthodox stance (left foot forward) and were right-handed. They underwent isokinetic testing of the knee joint at various angular velocities in both eccentric and concentric modes, as well as concentric trunk rotation strength assessments.\u003c/p\u003e\n\u003cp\u003ePrior to formal testing, basic anthropometric and training-related information was collected. The following measurements were recorded: training experience, age, height, body mass, BMI, waist circumference, hip circumference, waist-to-hip ratio, limb segment lengths, thigh circumference, and calf length. The group characteristics were as follows (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD):\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eAge: 16.82\u0026thinsp;\u0026plusmn;\u0026thinsp;1.83 years\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eTraining experience: 3.45\u0026thinsp;\u0026plusmn;\u0026thinsp;1.86 years\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eHeight: 168.18\u0026thinsp;\u0026plusmn;\u0026thinsp;5.30 cm\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eBody mass: 59.73\u0026thinsp;\u0026plusmn;\u0026thinsp;7.67 kg\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eWaist-to-hip ratio: 0.80\u0026thinsp;\u0026plusmn;\u0026thinsp;0.025\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eBMI: 21.06\u0026thinsp;\u0026plusmn;\u0026thinsp;1.98 kg/m\u0026sup2;\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eThigh circumference: 54.46\u0026thinsp;\u0026plusmn;\u0026thinsp;2.84 cm\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eCalf length: 37.91\u0026thinsp;\u0026plusmn;\u0026thinsp;2.77 cm\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eA priori power analysis was conducted for the paired-samples t-test (left vs. right side comparison) using G*Power 3.1.9.2 software (\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e). Parameters were set as follows: expected effect size Cohen's d_z\u0026thinsp;=\u0026thinsp;0.5 (medium effect, representing the minimum clinically meaningful difference), two-tailed \u0026alpha;\u0026thinsp;=\u0026thinsp;0.05, and desired statistical power (1-\u0026beta;)\u0026thinsp;=\u0026thinsp;0.95. The analysis indicated that a minimum sample size of n\u0026thinsp;=\u0026thinsp;16 was required (achieved power\u0026thinsp;=\u0026thinsp;0.955). In the actual study, observed effect sizes ranged from medium to large (Cohen's d\u0026thinsp;=\u0026thinsp;0.5\u0026ndash;1.37), confirming that the sample size was sufficient to detect true differences with adequate statistical power.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003ch2\u003e1.2 Data Processing\u003c/h2\u003e\n\u003cp\u003eAll data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD). Prior to statistical analysis, the normality of distribution was assessed using the Shapiro-Wilk test, and homogeneity of variances was evaluated with Levene\u0026rsquo;s test. For bilateral comparisons (left vs. right rotation / left vs. right knee), paired-samples t-tests were employed when data met the assumption of normality; otherwise, the non-parametric Wilcoxon signed-rank test was applied. Comparisons across different angular velocities were performed using repeated-measures analysis of variance (repeated measures ANOVA). When the assumption of sphericity was violated (Mauchly\u0026rsquo;s test, P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), degrees of freedom were corrected using either the Greenhouse-Geisser or Huynh-Feldt epsilon adjustment, as appropriate. Post-hoc pairwise comparisons were conducted with Bonferroni correction to control for multiple comparisons. Effect sizes were reported using Cohen\u0026rsquo;s d_z for paired comparisons, with the following interpretive guidelines: d_z\u0026thinsp;=\u0026thinsp;0.2 (small), 0.5 (medium), and 0.8 (large).The significance level was set at \u0026alpha;\u0026thinsp;=\u0026thinsp;0.05 (two-tailed) for all tests. All statistical analyses were conducted using SPSS version 26.0 (IBM Corp., Armonk, NY, USA).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"2 Data Collection","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Testing Procedure\u003c/h2\u003e \u003cp\u003eThe IsoMed 2000 isokinetic testing system was powered on and calibrated. The dynamometer head was rotated 180\u0026deg; around the chair to initiate automatic startup of the main console screen. Each of the 16 athletes was assigned a unique identifier (boxer01 to boxer16). In the patient interface, basic information\u0026mdash;including athlete code, date of birth, height, body mass, and other relevant details\u0026mdash;was entered and saved. To retrieve or edit an athlete\u0026rsquo;s profile or select testing protocols, the corresponding athlete number was entered directly into the system.\u003c/p\u003e \u003cp\u003eAfter retrieving the athlete\u0026rsquo;s information and exiting via the ESC key, the main testing interface was accessed. From the drop-down menu under test items, \u0026ldquo;Knee\u0026rdquo; or \u0026ldquo;Back\u0026rdquo; was selected and confirmed with the Enter key. \u0026ldquo;R\u0026rdquo; or \u0026ldquo;L\u0026rdquo; indicated right or left knee, respectively. In the movement mode interface, concentric (CON) or eccentric (ECC) testing was selected as M1 (flexion) or M2 (extension) actions. For concentric testing, identical contraction directions were chosen bilaterally (M1 CON, M2 CON); for eccentric testing, the corresponding modes were M1 ECC and M2 ECC. Angular velocities were set at 60\u0026deg;/s, 120\u0026deg;/s, and 180\u0026deg;/s, with 3 sets of 7 repetitions per velocity, an inter-set rest interval of 1 minute, and gravity compensation activated.\u003c/p\u003e \u003cp\u003e \u003cb\u003eKnee joint isokinetic strength testing\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe adjustable chair was configured with a backrest angle of 75\u0026deg; and a seat slide position of 12 mm forward. The athlete was seated in the appropriate position, and the dynamometer head height was adjusted. The infrared alignment marker was centered over the lateral femoral condyle to ensure accurate joint axis alignment. The shank was aligned parallel to the lever arm and secured just proximal to the ankle joint using straps. The upper body was stabilized with shoulder pads, and a wide waist belt was fastened around the pelvis. Both hands rested naturally on the side handles. The range of motion was set to 15\u0026deg;\u0026ndash;105\u0026deg; (or 90\u0026deg; excursion, locked via button controls).\u003c/p\u003e \u003cp\u003eDuring testing, the lever arm returned to the initial horizontal position, followed by a countdown. Prior to formal testing, athletes performed 3 submaximal familiarization trials at each target velocity while visually tracking the real-time torque feedback line on the monitor screen. Verbal encouragement was provided to ensure they reached the target line. Formal testing proceeded at 60\u0026deg;/s, 120\u0026deg;/s, and 180\u0026deg;/s, with 7 maximal repetitions per velocity. The highest peak torque and peak power values were recorded for analysis.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTrunk rotation isokinetic strength testing\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe dynamometer head was connected to the trunk rotation attachment. Athletes were seated with the knees secured using the adjustable knee fixation buttons to achieve comfortable, pain-free lower limb stabilization. The shoulder pads were adjusted for optimal comfort and secure fixation. The lever arm began in the initial leftward position, followed by a countdown.\u003c/p\u003e \u003cp\u003eBefore formal testing, athletes completed 3 submaximal familiarization trials at each target velocity, again tracking the on-screen torque cue line with verbal encouragement to reach the designated threshold. Formal testing was conducted at 60\u0026deg;/s, 120\u0026deg;/s, and 180\u0026deg;/s, with 7 maximal repetitions per velocity. Peak torque, total work, and other relevant parameters were recorded.\u003c/p\u003e \u003cp\u003eAthletes were instructed to refrain from fatiguing training the day prior to testing. All participants read and signed an informed consent form before commencement. Each testing session was preceded by a 15-minute standardized warm-up. If any discomfort or issue arose during testing, the athlete was instructed to verbally signal \u0026ldquo;stop,\u0026rdquo; upon which the experimenter immediately activated the emergency red stop button.\u003c/p\u003e \u003cp\u003eTesting was scheduled across multiple days to minimize fatigue effects, particularly from eccentric contractions:\u003c/p\u003e \u003cp\u003eDay 1: Left knee concentric testing\u003c/p\u003e \u003cp\u003eDay 2: Right knee concentric testing\u003c/p\u003e \u003cp\u003eDay 3: Left knee eccentric testing\u003c/p\u003e \u003cp\u003eDay 4: Right knee eccentric testing\u003c/p\u003e \u003cp\u003eDay 5: Trunk rotation testing\u003c/p\u003e \u003cp\u003eKnee joint testing followed an alternating-day protocol, with concentric assessments performed first, followed by eccentric assessments on subsequent days, to prevent carry-over fatigue from eccentric loading (see Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Selected Parameters\u003c/h2\u003e \u003cp\u003eThe following isokinetic strength parameters were selected for analysis:\u003c/p\u003e \u003cp\u003e1) Peak Torque (PT).Peak torque represents the highest torque value recorded on the torque curve during each repetition. It is expressed in Newton-meters (N\u0026middot;m) and serves as the primary indicator of maximal muscle strength under isokinetic conditions.\u003c/p\u003e \u003cp\u003e2) Hamstring-to-Quadriceps Ratio (H/Q ratio).The H/Q ratio is calculated as the ratio of hamstring (flexor) peak torque to quadriceps (extensor) peak torque, expressed as a percentage (%). This index reflects the strength balance between agonist and antagonist muscle groups surrounding the knee joint. A marked imbalance in this ratio may compromise joint stability and increase the risk of injury, particularly to the anterior cruciate ligament and other knee structures.\u003c/p\u003e \u003cp\u003e3) Total Work (TW) .Total work is defined as the cumulative area under the torque-time curve across the 7 repetitions of each set, representing the total mechanical work performed by the flexor and extensor muscle groups during the test. It is expressed in Joules (J) and provides an indirect measure of muscular endurance capacity.\u003c/p\u003e \u003cp\u003eClarification of Flexion and Extension Actions\u003c/p\u003e \u003cp\u003eEccentric (ECC) mode.The lever arm returns to the initial horizontal (extended) position at the start of the test. For eccentric quadriceps contraction (M2 ECC): The athlete resists the machine-driven flexion of the knee by eccentrically contracting the quadriceps while the lever arm moves downward.For eccentric hamstring contraction (M1 ECC): The athlete resists the machine-driven extension of the knee by eccentrically contracting the hamstrings as the lever arm moves upward to the extended position.\u003c/p\u003e \u003cp\u003eConcentric (CON) mode.The lever arm also returns to the initial horizontal (extended) position at the start of the test. For concentric hamstring contraction (M1 CON): The athlete actively flexes the knee, concentrically contracting the hamstrings to pull the lever arm downward. For concentric quadriceps contraction (M2 CON): The athlete actively extends the knee, concentrically contracting the quadriceps to push the lever arm upward to the extended position. In both modes, the dynamometer provides matching resistance throughout the entire range of motion, ensuring constant angular velocity.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and Analysis","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Analysis of Trunk Rotation Isokinetic Strength\u003c/h2\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (Trunk Rotation Peak Torque Statistics), at the slow velocity of 60\u0026deg;/s, peak torque (PT) of the left rotation muscle group was slightly higher than that of the right rotation group [86.39\u0026thinsp;\u0026plusmn;\u0026thinsp;19.95 N\u0026middot;m vs. 82.24\u0026thinsp;\u0026plusmn;\u0026thinsp;19.94 N\u0026middot;m], but the difference was not statistically significant (P\u0026thinsp;=\u0026thinsp;0.154).\u003c/p\u003e \u003cp\u003eAt 120\u0026deg;/s, left rotation peak torque was significantly greater than right rotation [110.30\u0026thinsp;\u0026plusmn;\u0026thinsp;21.37 N\u0026middot;m vs. 99.72\u0026thinsp;\u0026plusmn;\u0026thinsp;18.18 N\u0026middot;m; paired t-test, t\u0026thinsp;=\u0026thinsp;3.21, P\u0026thinsp;=\u0026thinsp;0.006, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.802]. Similarly, at 180\u0026deg;/s, the left-side advantage remained significant [77.15\u0026thinsp;\u0026plusmn;\u0026thinsp;28.97 N\u0026middot;m vs. 62.03\u0026thinsp;\u0026plusmn;\u0026thinsp;23.58 N\u0026middot;m; t\u0026thinsp;=\u0026thinsp;3.45, P\u0026thinsp;=\u0026thinsp;0.003, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.862].\u003c/p\u003e \u003cp\u003eRepeated-measures analysis of variance (Repeated Measures ANOVA) revealed a significant main effect of velocity on total work (TW) [F(1.45, 21.75)\u0026thinsp;=\u0026thinsp;28.74, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, partial η\u0026sup2; = 0.66], indicating a substantial overall difference in trunk rotational work output across angular velocities. Bonferroni post-hoc pairwise comparisons showed that total work at both 120\u0026deg;/s and 180\u0026deg;/s was significantly lower than at 60\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), while no significant difference was observed between 120\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eIn summary, concentric trunk rotation peak torque and relative torque exhibit clear velocity-dependent and lateral asymmetry characteristics. At slow speeds, bilateral values are comparable, whereas at moderate-to-high velocities the left rotation (dominant side) advantage becomes markedly pronounced, with effect sizes ranging from medium to large. These findings suggest that the functional superiority of the dominant (left-rotating) muscle group is particularly evident during explosive force production and high-velocity endurance tasks.\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\u003eTrunk Rotation Peak Torque Statistics (Unit: N\u0026middot;m)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTesting Mode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAngular Velocity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight Rotation Muscle Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft Rotation Muscle Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eConcentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e82.24\u0026thinsp;\u0026plusmn;\u0026thinsp;19.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e86.39\u0026thinsp;\u0026plusmn;\u0026thinsp;19.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.154\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e99.72\u0026thinsp;\u0026plusmn;\u0026thinsp;18.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e110.30\u0026thinsp;\u0026plusmn;\u0026thinsp;21.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.006*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e62.03\u0026thinsp;\u0026plusmn;\u0026thinsp;23.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e77.15\u0026thinsp;\u0026plusmn;\u0026thinsp;28.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.003*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eNote: indicates statistical significance at P\u0026thinsp;\u0026lt;\u0026thinsp;0.01.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Analysis of Trunk Rotation Isokinetic Strength (continued)\u003c/h2\u003e \u003cp\u003eAs presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (Trunk Rotation Total Work Statistics), total work (TW) reflects the cumulative mechanical work performed across the seven repetitions and serves as an indirect indicator of muscular endurance capacity.\u003c/p\u003e \u003cp\u003eThe results demonstrated that at the moderate velocity of 120\u0026deg;/s, total work of the left rotation muscle group was significantly greater than that of the right rotation group [418.758\u0026thinsp;\u0026plusmn;\u0026thinsp;74.26 J vs. 355.36\u0026thinsp;\u0026plusmn;\u0026thinsp;78.85 J; paired t-test, P\u0026thinsp;=\u0026thinsp;0.001, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.93]. This indicates superior power output and work capacity of the left (dominant) rotators at this velocity.\u003c/p\u003e \u003cp\u003eAt the high velocity of 180\u0026deg;/s, the bilateral difference in total work remained highly significant (left rotation: 284.73\u0026thinsp;\u0026plusmn;\u0026thinsp;98.29 J vs. right rotation: 228.12\u0026thinsp;\u0026plusmn;\u0026thinsp;78.02 J; P\u0026thinsp;=\u0026thinsp;0.001, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;1.37, large effect size), further highlighting a more pronounced lateral asymmetry during high-speed endurance tasks.\u003c/p\u003e \u003cp\u003eRepeated-measures analysis of variance (ANOVA) confirmed a significant main effect of velocity on total work [F(1.45, 21.75)\u0026thinsp;=\u0026thinsp;28.74, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, η\u0026sup2; = 0.66]. Bonferroni-adjusted post-hoc comparisons revealed that total work at both 120\u0026deg;/s and 180\u0026deg;/s was significantly lower than at 60\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), whereas no significant difference existed between 120\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eIn summary, as angular velocity increases, trunk rotational muscle endurance exhibits a clear dominant-side (left rotation) advantage. This asymmetry becomes particularly evident in the moderate-to-high velocity range (120\u0026deg;/s and 180\u0026deg;/s), where the left rotators consistently produce significantly greater total work than the right rotators. These findings suggest that sport-specific training programs should address this bilateral imbalance to optimize core endurance and fatigue resistance in adolescent female amateur boxers.\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\u003eTrunk Rotation Total Work Statistics (Unit: Joules, J)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTesting Mode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAngular Velocity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRight Rotation Muscle Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeft Rotation Muscle Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eConcentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e363.79\u0026thinsp;\u0026plusmn;\u0026thinsp;93.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e384.67\u0026thinsp;\u0026plusmn;\u0026thinsp;95.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.145\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e355.36\u0026thinsp;\u0026plusmn;\u0026thinsp;78.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e418.76\u0026thinsp;\u0026plusmn;\u0026thinsp;74.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e228.12\u0026thinsp;\u0026plusmn;\u0026thinsp;78.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e284.73\u0026thinsp;\u0026plusmn;\u0026thinsp;98.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eNote: indicates statistical significance at P\u0026thinsp;\u0026lt;\u0026thinsp;0.01. Values are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Analysis of Knee Joint Concentric and Eccentric Isokinetic Strength\u003c/h2\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (Descriptive Statistics for Knee Flexor and Extensor Peak Torque), knee joint muscle peak torque (PT) under concentric (CON) and eccentric (ECC) modes exhibited clear differences related to contraction type and pronounced velocity dependence.\u003c/p\u003e \u003cp\u003eConcentric contraction (CON) results\u003c/p\u003e \u003cp\u003eRepeated-measures ANOVA revealed a significant main effect of velocity [F(1.38, 20.70)\u0026thinsp;=\u0026thinsp;45.67, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, η\u0026sup2; = 0.75], indicating that PT decreased significantly with increasing angular velocity. Bonferroni post-hoc comparisons confirmed that PT at 60\u0026deg;/s was significantly higher than at both 120\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), while the difference between 120\u0026deg;/s and 180\u0026deg;/s approached significance (P\u0026thinsp;=\u0026thinsp;0.08).\u003c/p\u003e \u003cp\u003eAt the slow velocity of 60\u0026deg;/s, extensor PT reached its highest values bilaterally (right knee: 143.78\u0026thinsp;\u0026plusmn;\u0026thinsp;20.91 N\u0026middot;m; left knee: 141.87\u0026thinsp;\u0026plusmn;\u0026thinsp;22.40 N\u0026middot;m), with flexor PT being considerably lower (right knee: 83.39\u0026thinsp;\u0026plusmn;\u0026thinsp;15.72 N\u0026middot;m; left knee: 85.39\u0026thinsp;\u0026plusmn;\u0026thinsp;10.76 N\u0026middot;m). No significant bilateral differences were observed at this velocity (paired t-tests, all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eAs velocity increased to 120\u0026deg;/s, right-side flexor and extensor PT became significantly higher than the left side [flexors: t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;2.31, P\u0026thinsp;=\u0026thinsp;0.032, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.58; extensors: t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;2.14, P\u0026thinsp;=\u0026thinsp;0.044, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.54], suggesting the emergence of a right-side advantage at moderate velocities. At the highest velocity of 180\u0026deg;/s, PT values further declined and bilateral differences disappeared (all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eEccentric contraction (ECC) results: Repeated-measures ANOVA showed a significant main effect of velocity [F(1.62, 24.30)\u0026thinsp;=\u0026thinsp;12.89, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, partial η\u0026sup2; = 0.46; Greenhouse-Geisser correction applied], indicating overall differences in ECC PT across velocities. Bonferroni post-hoc tests revealed the largest difference between 60\u0026deg;/s and 120\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), while no significant difference was found between 120\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eEccentric strength was significantly greater than concentric strength across conditions (paired t-tests, overall P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), consistent with the well-established physiological principle that eccentric muscle actions produce higher force output than concentric actions.\u003c/p\u003e \u003cp\u003eIn eccentric flexion actions (quadriceps resisting machine-driven knee flexion), right-side quadriceps PT was significantly higher than the left side at all three velocities: 60\u0026deg;/s: 177.27\u0026thinsp;\u0026plusmn;\u0026thinsp;47.82 N\u0026middot;m vs. 162.30\u0026thinsp;\u0026plusmn;\u0026thinsp;41.23 N\u0026middot;m [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;4.12, P\u0026thinsp;=\u0026thinsp;0.001, d_z\u0026thinsp;=\u0026thinsp;1.03],120\u0026deg;/s: 204.15\u0026thinsp;\u0026plusmn;\u0026thinsp;56.82 N\u0026middot;m vs. 190.09\u0026thinsp;\u0026plusmn;\u0026thinsp;62.94 N\u0026middot;m [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;3.89, P\u0026thinsp;=\u0026thinsp;0.001, d_z\u0026thinsp;=\u0026thinsp;0.97],180\u0026deg;/s: 189.18\u0026thinsp;\u0026plusmn;\u0026thinsp;47.29 N\u0026middot;m vs. 166.79\u0026thinsp;\u0026plusmn;\u0026thinsp;49.80 N\u0026middot;m [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;4.56, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, d_z\u0026thinsp;=\u0026thinsp;1.14]\u003c/p\u003e \u003cp\u003eThe largest asymmetry was observed at 120\u0026deg;/s (maximum right-side value: 204.15 N\u0026middot;m). In contrast, during eccentric extension actions (hamstrings resisting machine-driven knee extension), no significant bilateral differences were detected (all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eThese findings indicate that the right quadriceps muscle group demonstrates a marked eccentric advantage during the braking phase, likely attributable to the repeated sport-specific loading experienced by the rear (right) leg in boxing\u0026mdash;particularly during push-off, deceleration, and rapid recovery phases\u0026mdash;resulting in enhanced eccentric tolerance and strength on the dominant side.\u003c/p\u003e \u003cp\u003eSummary. Under concentric conditions, knee muscle strength is dominated by slow-velocity absolute force production, with a right-side advantage emerging at moderate velocities. In eccentric mode, the right quadriceps (ECC flexion action) exhibits a more pronounced and consistent superiority across all tested velocities. These patterns suggest that boxing-specific training imparts a selective reinforcement of eccentric control capacity in the rear leg, particularly for the quadriceps muscle group.\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\u003eDescriptive Statistics for Knee Flexor and Extensor Peak Torque (PT) (Unit: N\u0026middot;m)\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 \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTesting Mode\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eAngular Velocity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eFlexion Action\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eExtension Action\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft Knee\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight Knee\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLeft Knee\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eRight Knee\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eConcentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e85.39\u0026thinsp;\u0026plusmn;\u0026thinsp;10.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e83.39\u0026thinsp;\u0026plusmn;\u0026thinsp;15.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e141.87\u0026thinsp;\u0026plusmn;\u0026thinsp;22.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e143.78\u0026thinsp;\u0026plusmn;\u0026thinsp;20.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.459\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e74.64\u0026thinsp;\u0026plusmn;\u0026thinsp;7.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e78.42\u0026thinsp;\u0026plusmn;\u0026thinsp;11.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.032*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e121.97\u0026thinsp;\u0026plusmn;\u0026thinsp;10.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e126.00\u0026thinsp;\u0026plusmn;\u0026thinsp;15.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.044*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e71.76\u0026thinsp;\u0026plusmn;\u0026thinsp;7.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e71.36\u0026thinsp;\u0026plusmn;\u0026thinsp;13.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.842\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e103.30\u0026thinsp;\u0026plusmn;\u0026thinsp;9.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e105.00\u0026thinsp;\u0026plusmn;\u0026thinsp;14.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.349\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eEccentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e162.30\u0026thinsp;\u0026plusmn;\u0026thinsp;41.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e177.27\u0026thinsp;\u0026plusmn;\u0026thinsp;47.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e105.09\u0026thinsp;\u0026plusmn;\u0026thinsp;20.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e101.88\u0026thinsp;\u0026plusmn;\u0026thinsp;20.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.138\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e190.09\u0026thinsp;\u0026plusmn;\u0026thinsp;62.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e204.15\u0026thinsp;\u0026plusmn;\u0026thinsp;56.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e109.42\u0026thinsp;\u0026plusmn;\u0026thinsp;25.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e105.61\u0026thinsp;\u0026plusmn;\u0026thinsp;28.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.067\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e166.79\u0026thinsp;\u0026plusmn;\u0026thinsp;49.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e189.18\u0026thinsp;\u0026plusmn;\u0026thinsp;47.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e104.00\u0026thinsp;\u0026plusmn;\u0026thinsp;21.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e103.82\u0026thinsp;\u0026plusmn;\u0026thinsp;25.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.928\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eNote: In concentric mode, flexion action represents active hamstring (flexor) work, and extension action represents active quadriceps (extensor) work. In eccentric mode, flexion action represents quadriceps resisting machine flexion (eccentric quadriceps),and extension action represents hamstrings resisting machine extension (eccentric hamstrings). indicates statistical significance at P\u0026thinsp;\u0026lt;\u0026thinsp;0.01. Values are mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAs presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (Knee Flexor and Extensor Total Work Statistics), total work (TW) of the knee muscle groups under concentric (CON) and eccentric (ECC) modes exhibited distinct differences in contraction type and clear patterns of lateral asymmetry.\u003c/p\u003e \u003cp\u003eConcentric contraction (CON) results: Repeated-measures ANOVA revealed a significant main effect of velocity on total work [F(1.32, 19.80)\u0026thinsp;=\u0026thinsp;38.56, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, η\u0026sup2; = 0.72], indicating a substantial decline in TW with increasing angular velocity. Bonferroni post-hoc comparisons confirmed that TW at 60\u0026deg;/s was significantly higher than at both 120\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), while no significant difference was observed between 120\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eAt the slow velocity of 60\u0026deg;/s, total work of the left knee flexors was significantly greater than the right (549.24\u0026thinsp;\u0026plusmn;\u0026thinsp;71.01 J vs. 498.39\u0026thinsp;\u0026plusmn;\u0026thinsp;110.45 J; paired t-test, t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;3.28, P\u0026thinsp;=\u0026thinsp;0.005, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.82, large effect size), suggesting superior flexor endurance on the left side at low velocities. In contrast, extensor total work showed no significant bilateral difference (P\u0026thinsp;=\u0026thinsp;0.336). As velocity increased to 120\u0026deg;/s and 180\u0026deg;/s, bilateral differences in both flexor and extensor total work disappeared (all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eEccentric contraction (ECC) results: Repeated-measures ANOVA demonstrated a significant main effect of velocity [F(1.58, 23.70)\u0026thinsp;=\u0026thinsp;14.23, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, η\u0026sup2; = 0.49], indicating overall differences in ECC total work across velocities. Bonferroni post-hoc tests showed that TW at 120\u0026deg;/s was significantly higher than at both 60\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), whereas no significant difference existed between 60\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eTotal work in ECC mode was significantly greater than in CON mode across conditions (paired t-tests, overall P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), consistent with the physiological characteristic that eccentric contractions produce higher mechanical work output.\u003c/p\u003e \u003cp\u003eIn eccentric flexion actions (quadriceps resisting machine-driven knee flexion), right-side quadriceps total work was significantly higher than the left side at all three velocities: 60\u0026deg;/s: 889.76\u0026thinsp;\u0026plusmn;\u0026thinsp;292.17 J vs. 839.12\u0026thinsp;\u0026plusmn;\u0026thinsp;223.87 J [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;2.35, P\u0026thinsp;=\u0026thinsp;0.032, d_z\u0026thinsp;=\u0026thinsp;0.59]. 120\u0026deg;/s: 1054.97\u0026thinsp;\u0026plusmn;\u0026thinsp;377.22 J vs. 976.69\u0026thinsp;\u0026plusmn;\u0026thinsp;348.69 J [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;3.12, P\u0026thinsp;=\u0026thinsp;0.005, d_z\u0026thinsp;=\u0026thinsp;0.78]. 180\u0026deg;/s: 947.18\u0026thinsp;\u0026plusmn;\u0026thinsp;313.16 J vs. 820.09\u0026thinsp;\u0026plusmn;\u0026thinsp;299.68 J [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;3.78, P\u0026thinsp;=\u0026thinsp;0.001, d_z\u0026thinsp;=\u0026thinsp;0.95].The largest right-side advantage occurred at 120\u0026deg;/s (peak value: 1054.97 J), highlighting prominent endurance superiority of the right quadriceps during eccentric braking phases. In eccentric extension actions (hamstrings resisting machine-driven knee extension), a significant bilateral difference was observed only at 60\u0026deg;/s, with right-side total work lower than left (t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) = \u0026minus;\u0026thinsp;3.45, P\u0026thinsp;=\u0026thinsp;0.003, d_z = \u0026minus;\u0026thinsp;0.86); no significant differences were found at the higher velocities (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eSummary. Under concentric conditions, knee muscle endurance is primarily characterized by slow-velocity absolute work capacity, with a notable left-side flexor advantage evident at low speeds. In eccentric mode, the right quadriceps muscle group (ECC flexion action) demonstrates markedly superior endurance across all tested velocities. These findings likely reflect adaptive responses to the sport-specific demands placed on the rear (right) leg in boxing, particularly during push-off, deceleration, and rapid leg recovery phases.\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\u003eKnee Flexor and Extensor Total Work Statistics (Unit: Joules, J)\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 \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTesting Mode\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eAngular Velocity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eFlexion Action (Hamstrings CON / Quadriceps ECC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eExtension Action (Quadriceps CON / Hamstrings ECC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft Knee\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight Knee\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLeft Knee\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eRight Knee\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eConcentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e549.24\u0026thinsp;\u0026plusmn;\u0026thinsp;71.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e498.39\u0026thinsp;\u0026plusmn;\u0026thinsp;110.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.005*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e802.42\u0026thinsp;\u0026plusmn;\u0026thinsp;108.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e772.60\u0026thinsp;\u0026plusmn;\u0026thinsp;162.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.336\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e501.87\u0026thinsp;\u0026plusmn;\u0026thinsp;61.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e492.27\u0026thinsp;\u0026plusmn;\u0026thinsp;89.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.483\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e743.66\u0026thinsp;\u0026plusmn;\u0026thinsp;69.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e755.18\u0026thinsp;\u0026plusmn;\u0026thinsp;113.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.351\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e430.30\u0026thinsp;\u0026plusmn;\u0026thinsp;45.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e394.21\u0026thinsp;\u0026plusmn;\u0026thinsp;93.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.022*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e624.54\u0026thinsp;\u0026plusmn;\u0026thinsp;62.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e620.12\u0026thinsp;\u0026plusmn;\u0026thinsp;111.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.784\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eEccentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e839.12\u0026thinsp;\u0026plusmn;\u0026thinsp;223.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e889.76\u0026thinsp;\u0026plusmn;\u0026thinsp;292.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.032*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e589.54\u0026thinsp;\u0026plusmn;\u0026thinsp;116.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e539.78\u0026thinsp;\u0026plusmn;\u0026thinsp;145.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.003*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e976.69\u0026thinsp;\u0026plusmn;\u0026thinsp;348.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1054.97\u0026thinsp;\u0026plusmn;\u0026thinsp;377.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.005*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e574.42\u0026thinsp;\u0026plusmn;\u0026thinsp;146.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e542.27\u0026thinsp;\u0026plusmn;\u0026thinsp;186.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.147\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e820.09\u0026thinsp;\u0026plusmn;\u0026thinsp;299.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e947.18\u0026thinsp;\u0026plusmn;\u0026thinsp;313.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e564.06\u0026thinsp;\u0026plusmn;\u0026thinsp;162.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e568.15\u0026thinsp;\u0026plusmn;\u0026thinsp;183.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.851\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/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Analysis of Hamstring-to-Quadriceps (H/Q) Peak Torque Ratio in Left and Right Knees\u003c/h2\u003e \u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (Knee Joint Peak Torque Hamstring-to-Quadriceps Ratio Statistics), the H/Q ratio under concentric (CON) and eccentric (ECC) modes exhibited distinct differences related to contraction type and velocity dependence, with pronounced bilateral asymmetry observed specifically in ECC mode.\u003c/p\u003e \u003cp\u003eConcentric contraction (CON) results. Repeated-measures ANOVA revealed a significant main effect of velocity on the H/Q ratio [F(1.42, 21.30)\u0026thinsp;=\u0026thinsp;18.45, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, η\u0026sup2; = 0.55], indicating a significant increase in H/Q with increasing angular velocity. Bonferroni post-hoc comparisons confirmed that the H/Q ratio at 180\u0026deg;/s was significantly higher than at both 60\u0026deg;/s and 120\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), while no significant difference was observed between 60\u0026deg;/s and 120\u0026deg;/s (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eIn CON mode, no statistically significant bilateral differences in H/Q ratios were detected at any tested velocity (paired t-tests, all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eEccentric contraction (ECC) results. Repeated-measures ANOVA showed no significant main effect of velocity on the H/Q ratio [F(1.68, 25.20)\u0026thinsp;=\u0026thinsp;2.34, P\u0026thinsp;=\u0026thinsp;0.118, η\u0026sup2; = 0.14], indicating that ECC H/Q ratios did not exhibit a clear overall trend across increasing velocities.\u003c/p\u003e \u003cp\u003eHowever, significant bilateral asymmetry was consistently observed: left-side H/Q ratios were significantly higher than right-side values at all three velocities: 60\u0026deg;/s: 66\u0026thinsp;\u0026plusmn;\u0026thinsp;12% vs. 59\u0026thinsp;\u0026plusmn;\u0026thinsp;12% [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;3.58, P\u0026thinsp;=\u0026thinsp;0.002, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.583].120\u0026deg;/s: 60\u0026thinsp;\u0026plusmn;\u0026thinsp;14% vs. 52\u0026thinsp;\u0026plusmn;\u0026thinsp;7% [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;4.01, P\u0026thinsp;=\u0026thinsp;0.001, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.70].180\u0026deg;/s: 65\u0026thinsp;\u0026plusmn;\u0026thinsp;15% vs. 55\u0026thinsp;\u0026plusmn;\u0026thinsp;9% [t(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u0026thinsp;=\u0026thinsp;4.12, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.765].This asymmetry progressively increased with velocity, reaching its maximum at the highest tested speed (180\u0026deg;/s), where the left-side H/Q exceeded the right-side value by approximately 10 percentage points. These findings suggest relatively greater eccentric strength of the right quadriceps and/or relatively weaker eccentric capacity of the left hamstrings under high-velocity conditions.\u003c/p\u003e \u003cp\u003eThe observed pattern reflects the asymmetric impact of boxing-specific training on knee muscle group balance. In adolescent amateur female athletes during a developmental stage, such eccentric bilateral imbalances may further amplify the risk of knee joint injuries, particularly anterior cruciate ligament strain or hamstring strain.\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\u003eKnee Joint Peak Torque Hamstring-to-Quadriceps (H/Q) Ratio Statistics (Unit: %)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTesting Mode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAngular Velocity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft Knee H/Q\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight Knee H/Q\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eConcentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e61\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e58\u0026thinsp;\u0026plusmn;\u0026thinsp;8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.115\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e61\u0026thinsp;\u0026plusmn;\u0026thinsp;6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e62\u0026thinsp;\u0026plusmn;\u0026thinsp;8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.464\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e69\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e68\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.548\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eEccentric\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e66\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e59\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.002*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e120\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e60\u0026thinsp;\u0026plusmn;\u0026thinsp;14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e52\u0026thinsp;\u0026plusmn;\u0026thinsp;7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e180\u0026deg;/s\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e65\u0026thinsp;\u0026plusmn;\u0026thinsp;15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e55\u0026thinsp;\u0026plusmn;\u0026thinsp;9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eNote: indicates statistical significance at P\u0026thinsp;\u0026lt;\u0026thinsp;0.01 (two-tailed paired t-test). Values are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. The H/Q ratio is calculated as (hamstring peak torque / quadriceps peak torque) \u0026times; 100%.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Trunk rotational strength and bilateral asymmetry\u003c/h2\u003e \u003cp\u003eThe present study revealed that in adolescent amateur female boxing athletes, concentric trunk axial rotation exhibited significant lateral asymmetry at moderate-to-high velocities: peak torque (PT) and total work (TW) of the left rotation (dominant side) were significantly greater than those of the right rotation at both 120\u0026deg;/s and 180\u0026deg;/s (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), with effect sizes ranging from medium to large (Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.50\u0026ndash;0.83). This asymmetry was not statistically significant at the slow velocity of 60\u0026deg;/s (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05) but progressively amplified with increasing angular velocity, suggesting that lateral differences are more functionally relevant during explosive power production (120\u0026deg;/s) and high-velocity endurance tasks (180\u0026deg;/s). This velocity-dependent pattern may reflect preferential recruitment of fast-twitch muscle fibers during higher-speed rotations, as well as stronger neuromuscular adaptations on the dominant side resulting from prolonged sport-specific training stimuli (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTrunk axial rotation constitutes a central component of the boxing punching kinetic chain, contributing 37\u0026ndash;42% to overall punch force generation (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). The observed left-rotation dominance is primarily attributable to the repetitive execution of rear-hand straight punches and hooks in the orthodox stance: forceful left rotation is driven predominantly by synergistic contraction of the left internal oblique, ipsilateral latissimus dorsi, and right external oblique muscles, whereas right rotation is more frequently utilized in defensive maneuvers, feints, or preparatory actions. This unilateral loading pattern aligns with asymmetry trends commonly reported in combat sports. Recent cross-disciplinary investigations in mixed martial arts (MMA) athletes have demonstrated strong correlations between trunk rotational strength and shoulder internal/external rotation, with asymmetries becoming particularly pronounced during alternating offensive-defensive sequences (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). In contrast, while unilateral-dominant sports such as tennis and golf also exhibit marked rotational asymmetries (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), the relative peak torque normalized to body weight observed in the present cohort at 120\u0026deg;/s (1.68\u0026ndash;1.87 N\u0026middot;m\u0026middot;kg⁻\u0026sup1;) is lower than values typically reported in trunk-dominant combat disciplines such as judo and wrestling (\u0026gt;\u0026thinsp;2.0 N\u0026middot;m\u0026middot;kg⁻\u0026sup1;). This difference underscores that punching performance in boxing relies more heavily on coordinated upper-limb kinetics and rapid torque transfer rather than maximal absolute rotational strength.\u003c/p\u003e \u003cp\u003eThe asymmetry observed here is likely a direct consequence of the long-term unilateral emphasis inherent in boxing training. The dominant (left-rotating) side is repeatedly trained for powerful, accurate, and aggressive punching, whereas the non-dominant (right-rotating) side is primarily engaged in probing, rapid directional changes, and defensive actions, resulting in substantial strength imbalance in the axial rotators. Under modern scoring systems that reward higher punch volume and frequent offensive-defensive transitions, this imbalance may be further exacerbated, as the dominant side bears a disproportionately higher cumulative load (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eExisting evidence indicates that rotational asymmetry can compromise dynamic spinal stability and is closely associated with lower back pain and lumbar injuries(\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). Although the cross-sectional design of the current study precludes causal inference, the combination of dominant-side overload and potential fatigue-induced declines in neuromuscular control\u0026mdash;such as reduced central drive and impaired proprioceptive input\u0026mdash;may elevate the risk of cumulative injury to the lumbar paraspinal muscles, latissimus dorsi, and associated structures, particularly during high-intensity sparring or competition scenarios involving rapid evasive maneuvers, hurried rotations, or missed punches. Prospective longitudinal studies are warranted to establish causality and track the temporal progression of these asymmetries.\u003c/p\u003e \u003cp\u003eTo mitigate this risk, future training interventions should prioritize bilateral symmetry development, with particular emphasis on strengthening right-sided anti-rotation and anti-lateral flexion exercises. Such targeted training may enhance spinal stability, improve core endurance under asymmetric loading, and reduce the long-term likelihood of lumbar injury in adolescent female amateur boxers.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Concentric Knee Strength Characteristics\u003c/h2\u003e \u003cp\u003eThe concentric (CON) testing results of the present study demonstrated that peak torque (PT) and total work (TW) of the knee extensor muscle group were significantly greater than those of the flexor group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01). All measured parameters reached their maximum values at the slowest angular velocity of 60\u0026deg;/s and declined markedly as velocity increased to 120\u0026deg;/s and 180\u0026deg;/s. This velocity-dependent reduction is consistent with the classic force-velocity relationship (Hill curve), wherein slow-velocity contractions primarily reflect maximal absolute strength (predominantly slow-twitch fiber recruitment and maximal neural drive), whereas higher velocities emphasize explosive power and muscular endurance (fast-twitch fiber recruitment with rapid fatigue and limited neural drive). This pattern has been extensively documented in lower-limb isokinetic assessments and represents a key characteristic for evaluating sport-specific strength profiles in athletes (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn bilateral comparisons, extensor PT at 60\u0026deg;/s was slightly higher on the right side than the left (143.78\u0026thinsp;\u0026plusmn;\u0026thinsp;20.91 N\u0026middot;m vs. 141.87\u0026thinsp;\u0026plusmn;\u0026thinsp;22.40 N\u0026middot;m), although the difference did not reach statistical significance (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, at the moderate velocity of 120\u0026deg;/s, both flexor and extensor PT were significantly greater on the right side compared to the left (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u0026ndash;0.01, Cohen\u0026rsquo;s d_z\u0026thinsp;\u0026asymp;\u0026thinsp;0.40\u0026ndash;0.55, medium effect sizes). This finding indicates a more pronounced right-side (rear-leg) advantage during moderate-velocity explosive force production. The observation aligns closely with the biomechanics of boxing in the orthodox stance: the rear (right) leg serves as the primary driver of ground reaction force and initiates momentum transfer for rear-hand straight punches and hooks. Prolonged repetitive training likely induces adaptive strength enhancements in the right quadriceps and hamstrings, resulting in sport-specific unilateral asymmetry(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eQuantitative comparisons revealed that the concentric knee flexor PT (83.39\u0026ndash;85.39 N\u0026middot;m) and extensor PT (141.87\u0026ndash;143.78 N\u0026middot;m) at 60\u0026deg;/s in the present cohort of adolescent amateur female boxers were substantially lower than values reported for female basketball players at comparable velocities [flexors: 115\u0026thinsp;\u0026plusmn;\u0026thinsp;21.03\u0026ndash;120.41\u0026thinsp;\u0026plusmn;\u0026thinsp;19.50 N\u0026middot;m; extensors: 188.82\u0026thinsp;\u0026plusmn;\u0026thinsp;59.37\u0026ndash;196.82\u0026thinsp;\u0026plusmn;\u0026thinsp;46.70 N\u0026middot;m], as well as recent data from amateur boxers [14]. Nevertheless, the values were higher than those typically observed in age-matched non-athletic female adolescents (quadriceps\u0026thinsp;\u0026asymp;\u0026thinsp;100 N\u0026middot;m; hamstrings\u0026thinsp;\u0026asymp;\u0026thinsp;55 N\u0026middot;m) [23]. These findings suggest that lower-limb absolute strength in amateur female boxers remains relatively modest, possibly due to training programs that prioritize technical-tactical repetition and sport-specific skill execution over high-intensity lower-body resistance training (particularly heavy squats, explosive leg drives, and eccentric loading). Compared with elite-level boxing or lower-limb dominant sports such as basketball, this relative strength deficit may limit the efficiency of kinetic chain momentum transfer during punching and increase the risk of compromised knee joint stability.\u003c/p\u003e \u003cp\u003eTo address this gap, it is recommended to incorporate dedicated lower-limb strength modules into training programs:\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Implement moderate-to-high velocity (120\u0026ndash;180\u0026deg;/s) isokinetic or isotonic squat and single-leg drive exercises to enhance right-side explosive power output;\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Prioritize strengthening of the non-dominant (left) side to prevent further amplification of existing asymmetry;\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Integrate plyometric training (e.g., box jumps, depth jumps) to specifically target velocity-dependent force production.\u003c/p\u003e \u003cp\u003eSuch targeted interventions are expected to optimize kinetic chain efficiency, improve punch force transmission, and reduce the potential for knee-related injury risk in this population.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Eccentric Knee Strength and Bilateral Differences\u003c/h2\u003e \u003cp\u003eIn eccentric (ECC) mode, knee joint muscle strength was significantly greater than in concentric (CON) mode (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), consistent with well-established physiological principles: eccentric contractions typically produce 1.2\u0026ndash;1.8 times greater force than concentric contractions. This enhanced force capacity arises primarily from stretch-reflex activation (increased muscle spindle sensitivity), passive elastic energy storage within the muscle-tendon unit (MTU), and preferential recruitment of type II fast-twitch fibers (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e). In boxing, this eccentric advantage is particularly critical, as defensive maneuvers, rapid directional changes, and landing impact absorption all rely on eccentric knee control to dissipate ground reaction forces, maintain postural stability, and prevent knee hyperextension or anterior cruciate ligament (ACL) injury.\u003c/p\u003e \u003cp\u003eThe present findings demonstrated that, during ECC testing, right-side flexor group performance (hamstrings resisting machine-driven knee extension) exhibited significantly higher peak torque (PT) and total work (TW) compared to the left side (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01, Cohen\u0026rsquo;s d_z\u0026thinsp;\u0026asymp;\u0026thinsp;0.23\u0026ndash;0.46, small to medium effect sizes). This right-side superiority was most pronounced at the moderate velocity of 120\u0026deg;/s, where right quadriceps eccentric PT (resisting machine-driven knee flexion) reached 204.15\u0026thinsp;\u0026plusmn;\u0026thinsp;56.82 N\u0026middot;m. This pattern likely reflects sport-specific neuromuscular adaptations in orthodox-stance boxers: the rear (right) leg must exert powerful eccentric control following rear-hand punch delivery to stabilize the base of support, rapidly retract the center of mass, and absorb landing impact forces. Repeated exposure to these demands over time appears to selectively enhance eccentric tolerance and strength in the right hamstrings and quadriceps, resulting in a boxing-specific unilateral asymmetry(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCompared with CON mode, the substantially greater force output and work capacity in ECC mode (with TW peaking at 1054.97\u0026thinsp;\u0026plusmn;\u0026thinsp;377.22 J at 120\u0026deg;/s) underscore the potential efficacy of eccentric training for improving overall muscle strength and agonist-antagonist balance. Recent meta-analyses have shown that 4\u0026ndash;12 weeks of structured eccentric training can significantly increase knee joint PT and H/Q ratios (with improvements ranging from 10\u0026ndash;20%) and reduce the risk of hamstring strain injuries (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). Nonetheless, the dual-edged nature of eccentric loading must be carefully considered (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e): high-intensity eccentric contractions are known to induce delayed-onset muscle soreness (DOMS) and microscopic muscle damage (Z-line disruption, inflammatory responses) (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). In the presence of pre-existing right-side dominance, unmonitored eccentric loading could further exacerbate bilateral asymmetry and elevate the cumulative risk of overuse injury (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). Therefore, eccentric training protocols should incorporate strict intensity control (initially 70\u0026ndash;80% of 1RM), progressive overload, and comprehensive recovery strategies\u0026mdash;including foam rolling, static stretching, and nutritional support\u0026mdash;to minimize adverse effects.\u003c/p\u003e \u003cp\u003eOverall, while the right-side flexor dominance observed in ECC mode optimizes rear-leg braking and support function during punching sequences, it also highlights the need for targeted eccentric strengthening of the non-dominant (left) side. Such balanced eccentric training is recommended to restore bilateral symmetry, enhance knee joint stability, and reduce the long-term risk of knee-related injuries in adolescent amateur female boxers.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Hamstring-to-Quadriceps (H/Q) Ratios\u003c/h2\u003e \u003cp\u003eThe present study demonstrated that in concentric (CON) mode, the hamstring-to-quadriceps peak torque ratio (H/Q ratio) progressively increased with angular velocity across 60\u0026deg;/s, 120\u0026deg;/s, and 180\u0026deg;/s, with no statistically significant bilateral differences at any velocity (all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). This velocity-dependent increase aligns with well-established isokinetic testing patterns: quadriceps (extensor) strength declines more rapidly at higher velocities compared to the hamstrings (flexors), resulting in an elevated H/Q ratio (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e) (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e) (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn contrast, eccentric (ECC) mode revealed pronounced bilateral asymmetry, with left-side H/Q ratios significantly higher than right-side values at all tested velocities: 60\u0026deg;/s: 66\u0026thinsp;\u0026plusmn;\u0026thinsp;12% vs. 59\u0026thinsp;\u0026plusmn;\u0026thinsp;12% (P\u0026thinsp;=\u0026thinsp;0.002, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.583, medium effect size) ,120\u0026deg;/s: 60\u0026thinsp;\u0026plusmn;\u0026thinsp;14% vs. 52\u0026thinsp;\u0026plusmn;\u0026thinsp;7% (P\u0026thinsp;=\u0026thinsp;0.001, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.70, medium-to-large effect size),180\u0026deg;/s: 65\u0026thinsp;\u0026plusmn;\u0026thinsp;15% vs. 55\u0026thinsp;\u0026plusmn;\u0026thinsp;9% (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Cohen\u0026rsquo;s d_z\u0026thinsp;=\u0026thinsp;0.765, large effect size)\u003c/p\u003e \u003cp\u003eThe asymmetry intensified with increasing velocity, reaching its maximum at 180\u0026deg;/s. The H/Q ratio, defined as hamstring peak torque divided by quadriceps peak torque (expressed as a percentage), typically ranges from 30% to 90% in healthy populations and plays a critical role in maintaining knee joint stability (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). An inadequate agonist-antagonist balance can compromise dynamic knee control and increase the risk of ligamentous and muscular injuries. Conventional consensus holds that a low concentric H/Q ratio at 60\u0026deg;/s is strongly associated with anterior cruciate ligament (ACL) injury and hamstring strain risk (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the current cohort, the CON H/Q ratios at 60\u0026deg;/s fell below or at the lower end of the critical threshold, and were modestly lower than normative values reported for elite female athletes in other sports (e.g., 48\u0026ndash;70% in elite female basketball and volleyball players, with higher values in basketball groups (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e)). These findings suggest relative hamstring weakness compared to quadriceps strength in adolescent amateur female boxers, likely reflecting an overemphasis on quadriceps-dominant push-off actions during punching sequences, while hamstring reinforcement has received insufficient attention in training programs.\u003c/p\u003e \u003cp\u003eThe marked lateral asymmetry in ECC mode further exacerbates this imbalance: a higher left-side H/Q indicates relatively stronger eccentric hamstring performance on the left and/or greater eccentric quadriceps dominance on the right. This pattern is consistent with boxing-specific demands in the orthodox stance, where the rear (right) leg experiences substantial eccentric loading to absorb ground reaction forces, decelerate forward momentum, and rapidly retract the center of mass following rear-hand punch delivery. Prolonged exposure to these asymmetric demands appears to preferentially enhance eccentric quadriceps capacity on the dominant side, while hamstring eccentric strength lags behind. Recent investigations in female competitive athletes have similarly linked abnormal H/Q ratios\u0026mdash;particularly low functional eccentric/concentric ratios\u0026mdash;to elevated knee injury risk, with asymmetry amplifying the likelihood of ACL rupture or chronic hamstring strain in unilaterally dominant sports [15, 36] (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFrom a physiological perspective, deviations in the H/Q ratio often reflect impaired neuromuscular coordination: excessive quadriceps dominance may inhibit co-activation of the hamstrings, thereby reducing dynamic knee stability (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). During adolescence, such imbalances warrant particular caution, as hormonal fluctuations, delayed neuromuscular maturation, and training-induced biases can further magnify asymmetry (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo prevent potential knee joint injuries and optimize muscle group balance, the following targeted interventions are recommended:\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Prioritize eccentric hamstring strengthening exercises (e.g., Nordic hamstring curls, isokinetic eccentric training at 60\u0026ndash;120\u0026deg;/s; structured 4\u0026ndash;8-week protocols can increase H/Q ratios by 10\u0026ndash;15%);\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Incorporate functional neuromuscular training (e.g., single-leg landing deceleration tasks, agility ladder drills) to enhance agonist-antagonist coordination;\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Implement regular isokinetic monitoring of H/Q ratios\u0026mdash;particularly in ECC mode\u0026mdash;to detect and correct emerging bilateral discrepancies and guide individualized training adjustments.\u003c/p\u003e \u003cp\u003eThese strategies are expected not only to maintain H/Q ratios within a safer range (\u0026gt;\u0026thinsp;0.60\u0026ndash;0.65) but also to improve knee joint stability during rapid directional changes and braking maneuvers, thereby supporting long-term health and athletic performance in adolescent female amateur boxers.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e4.5 Integrated Implications for the Boxing Kinetic Chain and Injury Prevention\u003c/h2\u003e \u003cp\u003ePunching in boxing constitutes a sequential closed kinetic chain action involving the foot-ankle-knee-hip-trunk-upper limb segments (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). Ground reaction forces are generated through lower-limb drive, transmitted via knee extension and eccentric control to the hip, and subsequently amplified through trunk axial rotation\u0026mdash;particularly leftward rotation during dominant rear-hand punches\u0026mdash;before being efficiently converted into upper-limb impact force. The present findings demonstrate a highly synergistic pattern between left-dominant trunk rotation and right-side eccentric knee flexor superiority (right significantly greater than left, P\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Left trunk rotation provides the primary rotational torque, while right knee extension and eccentric braking ensure stable rear-leg support and rapid center-of-mass recovery, collectively forming an efficient force transmission pathway. This \u0026ldquo;dominant-side reinforcement\u0026rdquo; configuration is consistent with the biomechanical demands of orthodox-stance boxing, where rear-hand straight punches and hooks rely predominantly on right-leg push-off combined with leftward trunk rotation.\u003c/p\u003e \u003cp\u003eHowever, this specialized adaptation introduces substantial overload risk to the dominant side (left trunk rotators\u0026thinsp;+\u0026thinsp;right knee). Prolonged high-magnitude loading on these segments may predispose athletes to cumulative injury of the lumbar paraspinal muscles and latissimus dorsi, as well as increased susceptibility to anterior cruciate ligament (ACL) strain or hamstring injury at the knee. This observation aligns with kinetic chain compensation theory: functional deficits or imbalances in one segment amplify mechanical stress on proximal and distal links (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e) (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFatigue further exacerbates these asymmetry-related risks. Under conditions of reduced central neural drive, diminished muscle spindle sensitivity, and compromised proprioceptive input, trunk rotational excursion may increase uncontrollably, while eccentric knee braking capacity declines. Such neuromuscular impairment is particularly pronounced during competitive bouts or high-intensity training sessions involving rapid evasive maneuvers, hurried rotations, or missed punches, potentially leading to excessive joint loading and loss of dynamic stability (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). Compared with elite-level boxers, the adolescent amateur female cohort in this study exhibited lower absolute lower-limb strength and more pronounced asymmetry (larger effect sizes), likely reflecting developmental-stage training programs that overemphasize technical-tactical repetition while under-prioritizing balanced strength development. This imbalance may further heighten the long-term risk of knee joint and lumbar injuries.\u003c/p\u003e \u003cp\u003eOverall, while the observed kinetic chain synergy optimizes punching efficiency, the combination of dominant-side overload and non-dominant-side weakness creates a vulnerability that can evolve into an injury \u0026ldquo;perfect storm\u0026rdquo; under fatigue or high-intensity conditions. To mitigate these risks and enhance long-term athletic health, the following integrated training strategies are recommended:\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Implement bilateral trunk rotational balance training, with particular emphasis on right-side anti-rotation and anti-lateral flexion exercises (e.g., medicine ball rotational throws, cable wood chops, or Pallof presses).\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Strengthen non-dominant (left) knee eccentric capacity through targeted eccentric protocols (e.g., isokinetic eccentric training at 60\u0026ndash;120\u0026deg;/s or eccentric single-leg squats).\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Monitor and maintain hamstring-to-quadriceps (H/Q) ratios above 0.60\u0026ndash;0.65, prioritizing eccentric hamstring reinforcement (e.g., Nordic hamstring curls, glute-ham raises, or eccentric isokinetic hamstring exercises).\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) Conduct periodic isokinetic assessments to track asymmetry progression, integrate fatigue management strategies (e.g., avoiding consecutive high-load eccentric sessions), and incorporate adequate recovery periods.\u003c/p\u003e \u003cp\u003eThese interventions are expected not only to reduce the likelihood of lumbar and knee injuries but also to further enhance kinetic chain efficiency and punching performance. Future prospective longitudinal studies are needed to validate the long-term efficacy of these balanced training approaches in adolescent female amateur boxers.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusions and Practical Applications","content":"\u003cp\u003eThe present study demonstrates that adolescent amateur female boxing athletes exhibit significant asymmetries in trunk axial rotation (left\u0026thinsp;\u0026gt;\u0026thinsp;right) and knee joint eccentric strength (right flexors\u0026thinsp;\u0026gt;\u0026thinsp;left), accompanied by relatively low absolute lower-limb strength compared with athletes in similar combat sports. The pronounced bilateral differences in eccentric hamstring-to-quadriceps (H/Q) ratios further highlight an imbalance that may elevate the risk of overuse injuries to the dominant-side lumbar region and knee joint structures.\u003c/p\u003e \u003cp\u003eThese findings reflect sport-specific neuromuscular adaptations driven by the repetitive unilateral demands of orthodox-stance punching mechanics\u0026mdash;particularly rear-hand power generation involving right-leg drive and leftward trunk rotation\u0026mdash;while revealing potential vulnerabilities resulting from inadequate bilateral balance and insufficient emphasis on eccentric control and hamstring reinforcement during developmental training phases.\u003c/p\u003e \u003cp\u003e \u003cb\u003ePractical Applications\u003c/b\u003e \u003c/p\u003e \u003cp\u003eTo mitigate injury risk, enhance kinetic chain efficiency, and optimize long-term athletic performance, the following evidence-based training recommendations are proposed:\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003cb\u003eBalance trunk rotational strength\u003c/b\u003e\u003c/p\u003e \u003cp\u003eIncorporate targeted exercises to strengthen the non-dominant (right) rotators and improve anti-rotation/anti-lateral flexion capacity. Examples include medicine ball rotational throws, cable woodchoppers, Pallof presses, and landmine anti-rotation presses. Perform 2\u0026ndash;3 sessions per week, integrated with core stability drills (e.g., planks with perturbations, bird dogs), to reduce asymmetric lumbar loading and enhance spinal dynamic stability.\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e)\u003cb\u003eStrengthen non-dominant (left) knee rapid force production\u003c/b\u003e\u003c/p\u003e \u003cp\u003ePrioritize eccentric and concentric training of the left knee extensors and flexors to improve front-leg support function and coordination with rear-leg drive. Utilize isokinetic eccentric/concentric protocols (60\u0026ndash;180\u0026deg;/s) and plyometric exercises (e.g., single-leg box drops, lateral bounds, depth jumps with controlled landing). This targeted approach aims to reduce bilateral asymmetry, enhance overall lower-limb symmetry, and support more efficient force transmission during punching sequences.\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003cb\u003eOptimize hamstring-to-quadriceps (H/Q) ratio\u003c/b\u003e\u003c/p\u003e \u003cp\u003eImplement structured eccentric hamstring strengthening to elevate and maintain the H/Q ratio above 0.60\u0026ndash;0.65, particularly in eccentric mode. Key exercises include Nordic hamstring curls (progressive volume and load), glute-ham raises, and isokinetic eccentric hamstring training at 60\u0026ndash;120\u0026deg;/s. A 4\u0026ndash;8-week progressive program has been shown to yield meaningful improvements in H/Q ratios and reduce hamstring strain risk, while concurrently supporting anterior cruciate ligament protection.\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e)\u003cb\u003eRegular isokinetic monitoring and fatigue management\u003c/b\u003e\u003c/p\u003e \u003cp\u003eConduct periodic isokinetic assessments (every 8\u0026ndash;12 weeks) to track changes in bilateral asymmetry, velocity-dependent strength profiles, and H/Q ratios. Combine this surveillance with deliberate fatigue management strategies, such as avoiding consecutive high-intensity eccentric sessions, incorporating adequate recovery periods (48\u0026ndash;72 hours between heavy lower-limb sessions), and monitoring subjective fatigue markers. These measures will help minimize cumulative overload, prevent exacerbation of existing asymmetries, and sustain improvements in punching efficiency and injury resilience.\u003c/p\u003e \u003cp\u003eImplementation of these practical recommendations\u0026mdash;emphasizing bilateral symmetry, eccentric control, and ongoing monitoring\u0026mdash;offers a proactive framework to safeguard musculoskeletal health while simultaneously enhancing sport-specific performance in adolescent amateur female boxers. Longitudinal follow-up studies are encouraged to evaluate the long-term efficacy of these integrated interventions on injury incidence and competitive outcomes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of Shanghai University of Sport (approval number: 102772019RT033). The study was conducted in accordance with the Declaration of Helsinki. All participants provided written informed consent prior to their participation in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have approved this manuscript for publication. This manuscript has not previously been published and is not pending publication elsewhere.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYang Liu and Zhiyong Chen Writing– original draft, Writing – review \u0026amp; editing. Jian Xiao: Conceptualization, Methodology, Funding acquisition, Project administration .All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by the National-sponsored Social Sciences Funding Program (23BTY051).\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLiu YZ, Chen ZQ, Deng XX, Ma CY, Zhao XJ. Biomechanics of the lead straight punch of different level boxers. Front Physiol. 2022;13:1\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3389/fphys.2022.1015154\u003c/span\u003e\u003cspan address=\"https://doi:10.3389/fphys.2022.1015154\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFilimonov VI, Koptsev KN, Husyanov ZM et al. Boxing: Means of increasing strength of the punch. Natl Strength Conditioning Association J. 1985;7(6).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHislop HJ, Perrine JJ. The isokinetic concept of exercise. Phys Ther. 1967;47(2):114.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003evan der Woude DR, Ruyten T, Bartels B. Reliability of Muscle Strength and Muscle Power Assessments Using Isokinetic Dynamometry in Neuromuscular Diseases: A Systematic Review. Phys Ther. 2022;102(10). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1093/ptj/pzac099\u003c/span\u003e\u003cspan address=\"https://doi:10.1093/ptj/pzac099\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGu\u0026eacute;rin M, Sijobert B, Zaragoza B, Cambon F, Boyer L, Patte K. Combining Intensive Rehabilitation With a Nonfunctional Isokinetic Strengthening Program in Adolescents With Cerebral Palsy: Protocol for a Randomized Controlled Trial. JMIR Res protocols. 2023;12:e43221. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.2196/43221\u003c/span\u003e\u003cspan address=\"https://doi:10.2196/43221\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAyala F, De Ste Croix M, Sainz de Baranda P, Santonja F. Absolute reliability of isokinetic knee flexion and extension measurements adopting a prone position. Clin Physiol Funct Imaging. 2013;33(1):45\u0026ndash;54. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1111/j.1475-097X.2012.01162.x\u003c/span\u003e\u003cspan address=\"https://doi:10.1111/j.1475-097X.2012.01162.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang H, Guo J, Yang J, Jiang Y, Yu Y, M\u0026uuml;ller S, et al. Isokinetic angle-specific moments and ratios characterizing hamstring and quadriceps strength in anterior cruciate ligament deficient knees. Sci Rep. 2017;7(1):7269. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1038/s41598-017-06601-5\u003c/span\u003e\u003cspan address=\"https://doi:10.1038/s41598-017-06601-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKocahan T, Akınoğlu B. Determination of the relationship between core endurance and isokinetic muscle strength of elite athletes. J Exerc rehabilitation. 2018;14(3):413\u0026ndash;8. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.12965/jer.1836148.074\u003c/span\u003e\u003cspan address=\"https://doi:10.12965/jer.1836148.074\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen C, Ali Z, Rashid MAR, Samethanovna MU, Wu GD, Mukhametkali S, et al. Relationship between isokinetic strength of the knee joint and countermovement jump performance in elite boxers. PeerJ. 2023;11:1\u0026ndash;14. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.7717/peerj.16521\u003c/span\u003e\u003cspan address=\"https://doi:10.7717/peerj.16521\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrukner P, Nealon A, Morgan C, Burgess D, Dunn A. Recurrent hamstring muscle injury: applying the limited evidence in the professional football setting with a seven-point programme. Br J Sports Med. 2014;48(11):929\u0026ndash;38. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1136/bjsports-2012-091400\u003c/span\u003e\u003cspan address=\"https://doi:10.1136/bjsports-2012-091400\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTasiopoulos I, Nikolaidis PT, Tripolitsioti A, Stergioulas A, Rosemann T, Knechtle B. Isokinetic Characteristics of Amateur Boxer Athletes. Front Physiol. 2018;9:1597. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3389/fphys.2018.01597\u003c/span\u003e\u003cspan address=\"https://doi:10.3389/fphys.2018.01597\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTunstall H, Mullineaux DR, Vernon T. Criterion validity of an isokinetic dynamometer to assess shoulder function in tennis players. Sports Biomech. 2005;4(1):101\u0026ndash;11. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1080/14763140508522855\u003c/span\u003e\u003cspan address=\"https://doi:10.1080/14763140508522855\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu YL, Jiang L, Geng M. Comparative effects of unilateral, bilateral, and hybrid combined resistance training on straight punch performance in adolescent boxers: a focus on dominant and non-dominant-side adaptations. Eur J Appl Physiol. 2025. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1007/s00421-025-05913-z\u003c/span\u003e\u003cspan address=\"https://doi:10.1007/s00421-025-05913-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhou ZX, Chen C, Chen X, Yi WJ, Cui WJ, Wu R, et al. Lower extremity isokinetic strength characteristics of amateur boxers. Front Physiol. 2022;13. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3389/fphys.2022.898126\u003c/span\u003e\u003cspan address=\"https://doi:10.3389/fphys.2022.898126\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMyer GD, Sugimoto D, Thomas S, Hewett TE. The influence of age on the effectiveness of neuromuscular training to reduce anterior cruciate ligament injury in female athletes: a meta-analysis. Am J Sports Med. 2013;41(1):203\u0026ndash;15. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1177/0363546512460637\u003c/span\u003e\u003cspan address=\"https://doi:10.1177/0363546512460637\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFaul F, Erdfelder E, Lang A-G, Buchner A. G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007;39(2):175\u0026ndash;91. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3758/BF03193146\u003c/span\u003e\u003cspan address=\"https://doi:10.3758/BF03193146\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHank M, Miratsky P, Ford KR, Clarup C, Imal O, Verbruggen FF, et al. Exploring the interplay of trunk and shoulder rotation strength: a cross-sport analysis. Front Physiol. 2024;15:1371134. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3389/fphys.2024.1371134\u003c/span\u003e\u003cspan address=\"https://doi:10.3389/fphys.2024.1371134\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEllenbecker TS, Roetert EP. An isokinetic profile of trunk rotation strength in elite tennis players. Med Sci Sports Exerc. 2004;36(11):1959\u0026ndash;63. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1249/01.mss.0000145469.08559.0e\u003c/span\u003e\u003cspan address=\"https://doi:10.1249/01.mss.0000145469.08559.0e\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDavis P, Benson PR, Pitty JD, Connorton AJ, Waldock R. The Activity Profile of Elite Male Amateur Boxing. Int J Sport Physiol Perform. 2015;10(1):53\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1123/ijspp.2013-0474\u003c/span\u003e\u003cspan address=\"10.1123/ijspp.2013-0474\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi\u003c/span\u003e\u003cspan address=\"https://doi\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKumar S, Dufresne RM, Van Schoor T. Human trunk strength profile in lateral flexion and axial rotation. Spine. 1995;20(2):169\u0026ndash;77. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1097/00007632-199501150-00007\u003c/span\u003e\u003cspan address=\"https://doi:10.1097/00007632-199501150-00007\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDrouin JM, Valovich-mcLeod TC, Shultz SJ, Gansneder BM, Perrin DH. Reliability and validity of the Biodex system 3 pro isokinetic dynamometer velocity, torque and position measurements. Eur J Appl Physiol. 2004;91(1):22\u0026ndash;9. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1007/s00421-003-0933-0\u003c/span\u003e\u003cspan address=\"https://doi:10.1007/s00421-003-0933-0\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDong K, Yu T, Chun B. Effects of Core Training on Sport-Specific Performance of Athletes: A Meta-Analysis of Randomized Controlled Trials. Behavioral sciences (Basel, Switzerland). 2023;13(2). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3390/bs13020148\u003c/span\u003e\u003cspan address=\"https://doi:10.3390/bs13020148\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerzog W. Why are muscles strong, and why do they require little energy in eccentric action? J Sport Health Sci. 2018;7(3):255\u0026ndash;64. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1016/j.jshs.2018.05.005\u003c/span\u003e\u003cspan address=\"https://doi:10.1016/j.jshs.2018.05.005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYagiz G, Akaras E, Kubis HP, Owen JA. Heterogeneous effects of eccentric training and nordic hamstring exercise on the biceps femoris fascicle length based on ultrasound assessment and extrapolation methods: A systematic review of randomised controlled trials with meta-analyses. PLoS ONE. 2021;16(11):e0259821. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1371/journal.pone.0259821\u003c/span\u003e\u003cspan address=\"https://doi:10.1371/journal.pone.0259821\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAndroulakis Korakakis P, Wolf M, Coleman M, Burke R, Pi\u0026ntilde;ero A, Nippard J, et al. Optimizing Resistance Training Technique to Maximize Muscle Hypertrophy: A Narrative Review. J Funct morphology Kinesiol. 2023;9(1). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3390/jfmk9010009\u003c/span\u003e\u003cspan address=\"https://doi:10.3390/jfmk9010009\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStauber WT. Eccentric action of muscles: physiology, injury, and adaptation. Exerc Sport Sci Rev. 1989;17:157\u0026ndash;85.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShalmon G, Shapira G, Ibrahim R, Israel-Elgali I, Grad M, Shlayem R, et al. Maximal and sub-maximal exercise tests alter PBMC microRNA expression: insights into sport- and sex-specific variations. Front Physiol. 2025;16:1583870. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3389/fphys.2025.1583870\u003c/span\u003e\u003cspan address=\"https://doi:10.3389/fphys.2025.1583870\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeng Q, Su CH. The Impact of Physical Exercise on Oxidative and Nitrosative Stress: Balancing the Benefits and Risks. Antioxid (Basel Switzerland). 2024;13(5). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3390/antiox13050573\u003c/span\u003e\u003cspan address=\"https://doi:10.3390/antiox13050573\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArvanitidis M, Jim\u0026eacute;nez-Grande D, Haouidji-Javaux N, Falla D, Martinez-Valdes E. Eccentric exercise-induced delayed onset trunk muscle soreness alters high-density surface EMG-torque relationships and lumbar kinematics. Sci Rep. 2024;14(1):18589. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1038/s41598-024-69050-x\u003c/span\u003e\u003cspan address=\"https://doi:10.1038/s41598-024-69050-x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAagaard P, Simonsen EB, Andersen JL, Magnusson SP, Bojsen-M\u0026oslash;ller F, Dyhre-Poulsen P. Antagonist muscle coactivation during isokinetic knee extension. Scand J Med Sci Sports. 2000;10(2):58\u0026ndash;67. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1034/j.1600-0838.2000.010002058.x\u003c/span\u003e\u003cspan address=\"https://doi:10.1034/j.1600-0838.2000.010002058.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCoombs R, Garbutt G. Developments in the use of the hamstring/quadriceps ratio for the assessment of muscle balance. J sports Sci Med. 2002;1(3):56\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRemaud A, Cornu C, Gu\u0026eacute;vel A. Agonist muscle activity and antagonist muscle co-activity levels during standardized isotonic and isokinetic knee extensions. J Electromyogr kinesiology: official J Int Soc Electrophysiological Kinesiol. 2009;19(3):449\u0026ndash;58. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jelekin.2007.11.001\u003c/span\u003e\u003cspan address=\"10.1016/j.jelekin.2007.11.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi\u003c/span\u003e\u003cspan address=\"https://doi\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNosse LJ. Assessment of selected reports on the strength relationship of the knee musculature*. J Orthop Sports Phys Ther. 1982;4(2):1.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRuas CV, Pinto RS, Haff GG, Lima CD, Pinto MD, Brown LE. Alternative Methods of Determining Hamstrings-to-Quadriceps Ratios: a Comprehensive Review. Sports Med Open. 2019;5(1):11. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1186/s40798-019-0185-0\u003c/span\u003e\u003cspan address=\"https://doi:10.1186/s40798-019-0185-0\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKabacinski J, Murawa M, Mackala K, Dworak LB. Knee strength ratios in competitive female athletes. PLoS ONE. 2018;13(1):e0191077. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1371/journal.pone.0191077\u003c/span\u003e\u003cspan address=\"https://doi:10.1371/journal.pone.0191077\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKrosshaug T, Nakamae A, Boden BP, Engebretsen L, Smith G, Slauterbeck JR, et al. Mechanisms of anterior cruciate ligament injury in basketball: video analysis of 39 cases. Am J Sports Med. 2007;35(3):359\u0026ndash;67. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1177/0363546506293899\u003c/span\u003e\u003cspan address=\"https://doi:10.1177/0363546506293899\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTosarelli F, Buckthorpe M, Di Paolo S, Grassi A, Rodas G, Zaffagnini S, et al. Video Analysis of Anterior Cruciate Ligament Injuries in Male Professional Basketball Players: Injury Mechanisms, Situational Patterns, and Biomechanics. Orthop J sports Med. 2024;12(3):23259671241234880. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1177/23259671241234880\u003c/span\u003e\u003cspan address=\"https://doi:10.1177/23259671241234880\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHewett TE, Myer GD, Ford KR, Paterno MV, Quatman CE. Mechanisms, prediction, and prevention of ACL injuries: Cut risk with three sharpened and validated tools. J Orthop research: official publication Orthop Res Soc. 2016;34(11):1843\u0026ndash;55. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1002/jor.23414\u003c/span\u003e\u003cspan address=\"https://doi:10.1002/jor.23414\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu X, Sun Y, Zhu D. Analysis of the impact force and key technique of backward straight punch in different combat sports. Sci Rep. 2025;15(1):10958. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1038/s41598-025-96264-4\u003c/span\u003e\u003cspan address=\"https://doi:10.1038/s41598-025-96264-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSaeterbakken AH, Sandvikmoen TE, Iversen E, Bj\u0026oslash;rnsen T, Stien N, Andersen V, et al. The effect of heavy-resistance core strength training on upper-body strength and power performance in national-level junior athletes-a pilot study. Front Physiol. 2025;16:1617104. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.3389/fphys.2025.1617104\u003c/span\u003e\u003cspan address=\"https://doi:10.3389/fphys.2025.1617104\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSašek M, Šarabon N, Smajla D. Exploring the relationship between lower limb strength, strength asymmetries, and curvilinear sprint performance: Findings from a pilot study. Sci Prog. 2024;107(2):368504241247998. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi:10.1177/00368504241247998\u003c/span\u003e\u003cspan address=\"https://doi:10.1177/00368504241247998\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"isokinetic strength, trunk rotation, knee joint, asymmetry, female boxing, injury prevention, H/Q ratio","lastPublishedDoi":"10.21203/rs.3.rs-9121035/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9121035/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Objective: To investigate the asymmetry in trunk axial rotation and knee joint isokinetic strength characteristics among adolescent amateur female boxing athletes, providing guidance for sport-specific strength training and injury prevention.\nMethods: Sixteen adolescent amateur female boxing athletes [age 16.8 ± 1.8 years, height 168.2 ± 5.3 cm, body mass 59.7 ± 7.7 kg] were tested using the IsoMed 2000 isokinetic dynamometer. Knee joint concentric (CON) and eccentric (ECC) contractions, as well as trunk rotation concentric contractions, were assessed at angular velocities of 60°/s, 120°/s, and 180°/s, with 3 sets of 7 repetitions per velocity. Paired-samples t-tests were used to compare bilateral differences, and repeated-measures ANOVA was applied to evaluate velocity effects.\nResults: Trunk rotation concentric contractions exhibited significant velocity dependence and lateral asymmetry. Repeated-measures ANOVA revealed a significant main effect of velocity (P \u003c 0.001). At 120°/s and 180°/s, left rotation (dominant side) showed significantly higher PT and TW compared to right rotation (P \u003c 0.01, Cohen's d_z medium to large), whereas no significant difference was observed at the slower velocity of 60°/s. Knee joint eccentric strength was significantly greater than concentric strength (P \u003c 0.001). In ECC mode, right-side flexor group PT and TW were significantly higher than the left side (P \u003c 0.01), with a significant main effect of velocity (P \u003c 0.001). In CON mode, parameters peaked at 60°/s and decreased significantly with increasing velocity (P \u003c 0.001). The hamstring-to-quadriceps (H/Q) ratio showed no significant bilateral differences in CON mode (P \u003e 0.05), but in ECC mode, the left side was significantly higher than the right (P \u003c 0.01), with the asymmetry magnifying as velocity increased.\nConclusion: Adolescent amateur female boxing athletes demonstrate significant asymmetries in trunk rotation (left \u003e right) and knee joint muscle strength (ECC right flexors \u003e left), with stronger performance on the dominant side. These imbalances may elevate the risk of lumbar and knee injuries. Compared with similar studies on amateur boxers, lower limb absolute strength appears relatively low in the present cohort. It is recommended to implement balanced bilateral trunk rotational training, strengthen rapid force production in the non-dominant side, and optimize the H/Q ratio to enhance sport-specific performance and reduce injury risk.","manuscriptTitle":"Isokinetic strength characteristics of trunk rotation and knee joint in female amateur boxers: asymmetry and implications for injury prevention","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-23 13:59:32","doi":"10.21203/rs.3.rs-9121035/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-04-30T03:40:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"59240561958697380846586167653961262400","date":"2026-04-20T22:46:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-26T07:30:53+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"148762798589016753461191843658001265970","date":"2026-03-26T06:54:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"100751684207722436758966077837632563245","date":"2026-03-20T15:12:44+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-19T03:33:08+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-03-16T10:45:17+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-16T10:32:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-16T10:31:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2026-03-14T08:38:13+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"224dbbbc-a6f9-4e5a-819f-88f09082e047","owner":[],"postedDate":"March 23rd, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-04-30T03:40:33+00:00","index":48,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-23T13:59:32+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-23 13:59:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9121035","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9121035","identity":"rs-9121035","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}