The moderating role of age in the effect of hip and knee joint functions on explosive power performance in soccer players

The moderating role of age in the effect of hip and knee joint functions on explosive power performance in soccer players | 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 The moderating role of age in the effect of hip and knee joint functions on explosive power performance in soccer players Halil İbrahim Çakır, Recep Fatih Kayhan, Esranur Terzi, Harun Koç This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9372764/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background Explosive power is a key determinant of soccer performance and is closely associated with lower extremity joint function, particularly hip and knee range of motion (ROM) and muscle strength. These factors contribute to essential actions such as jumping, sprinting, and rapid changes of direction; however, their influence may vary across developmental stages due to age-related neuromuscular and physical differences. Despite existing evidence linking strength and flexibility to motor performance, the moderating role of age in these relationships remains unclear in youth soccer players. Therefore, this study aimed to investigate the effects of hip and knee joint ROM and muscle strength on motor performance and to evaluate the moderating role of age in these associations. Methods A total of 59 male football players from the youth academies of professional teams participated in the study. ROM values of the hip/knee joints, as well as quadriceps/hamstring muscle strength, were measured; subsequently, motor performance assessments were conducted. The data were analyzed using multiple regression models including interaction terms with age, and regions of significance were determined using the Johnson–Neyman technique. Results For the reactive strength index, hip and knee ROM and quadriceps strength were identified as significant predictors; however, these effects were particularly pronounced in soccer players under the age of 17–18 (r 2 = 0.076–0.239; p < 0.01). Similarly, for vertical and horizontal jump performance, hip and knee ROM, as well as quadriceps and hamstring muscle strength, were significant predictors, with these effects again being more evident in players under the age of 17–18 (r 2 = 0.061–0.553; p < 0.01). Conclusion Lower extremity physical characteristics influence motor performance in an age-dependent manner, with stronger effects observed in players under 17–18 years and reduced effects at older ages. Therefore, structuring training programs in these age groups to prioritize the development of range of motion and strength, integrated with exercises that support neuromuscular control, is of great importance for enhancing performance and reducing the risk of injury. Age differences Explosive power Neuromuscular performance Soccer players Youth athletes Introduction Soccer is a multidimensional sport in which anaerobic power, agility, balance, and a high level of neuromuscular coordination function collectively. By its very nature, the structure of the game involves short-duration, high-intensity efforts such as rapid changes of direction, sudden accelerations, jumping, and leaping. These performance demands cause the physical and neuromuscular characteristics of the lower extremities to play a decisive role in athletic success [ 1 ]. Within this framework, muscle strength—one of the key determinants of motor performance—emerges as a parameter subject to developmental changes with age [ 2 , 3 ]. In particular, the strength levels of the quadriceps and hamstring muscle groups play a critical role in performing high-intensity movements such as running, jumping, and change of direction in soccer players [ 4 ]. The strength capacity of these muscles is directly related to the effectiveness of eccentric and concentric contractions, as well as to the functionality of the stretch-shortening cycle [ 5 ]. In this context, the Reactive Strength Index (RSI) provides information about the duration and magnitude of power applied to the ground by utilizing the elastic properties of the muscle–tendon complex [ 6 ]. In this respect, RSI serves as a neuromechanical output of lower extremity strength and is a valuable indicator in predicting both vertical and horizontal jump performance [ 6 ]. While vertical jump assesses explosive power and the capacity to generate power against gravity, horizontal jump is an effective tool for evaluating forward power production and dynamic balance capacity [ 7 ]. Accordingly, the inclusion of both vertical and horizontal jump tests in our study enables the assessment of the multidirectional power production capacity of the lower extremities. In addition to muscle strength, joint range of motion (ROM) is another important determinant of motor performance [ 8 ]. Adequate ROM allows body segments to operate within optimal movement amplitudes, thereby contributing to the more efficient and controlled execution of motor tasks. Insufficient ROM, on the other hand, may lead to the development of compensatory strategies during movement, resulting in both performance decrements and an increased risk of injury. In particular, adequate range of motion in the hip and knee joints enables the kinetic chain to function effectively and synchronously during tasks such as sprinting, jumping, and changing direction [ 8 ]. One of the environmental and biological factors influencing the development of these physical characteristics is age. Neuromuscular changes occurring during adolescence lead to developmental differences in both muscle strength and motor control mechanisms, varying in rate and manner [ 8 ]. In this context, age groups (e.g., U15, U16, U17, U19) are likely to play a moderating role in the relationships between physical characteristics and motor performance. Although age-based analyses of this nature have been reported in the literature [ 9 – 11 ], studies that simultaneously address multiple physical characteristics such as ROM and muscle strength and test the effect of age on these relationships using multivariate models are limited [ 8 , 12 ]. The present study not only compares age groups in terms of motor performance but also provides a multivariate perspective by considering age together with physical variables such as ROM and strength. That is, in our research, age was examined within a framework in which performance was modeled and analyzed alongside other physical determinants. In this regard, the study presents an original structure that evaluates the developmental effects of physical characteristics in conjunction with age. From this perspective, the study has the potential to make significant contributions to subfields of sport sciences such as developmental physiology, performance analysis, and training planning. Accordingly, the aim of the present study is to examine, through multivariate models, the effects of lower extremity physical characteristics (muscle strength and joint range of motion) on motor performance indicators (RSI, vertical jump, and horizontal jump) in soccer players from different age groups and to reveal the moderating role of age in these relationships. In line with this objective, it was hypothesized that (i) age significantly affects the relationship between ROM and motor performance, and (ii) age significantly affects the relationship between muscle strength and motor performance. Materials and methods Study design This study was structured within a cross-sectional, regression-based moderation framework to elucidate the role of age in shaping the relationship between lower extremity physical attributes (muscle strength and joint ROM) and motor performance outcomes (RSI, vertical and horizontal jump) in youth soccer players. By integrating interaction terms into multivariate models, the design enabled a comprehensive evaluation of age-related differential effects under standardized laboratory conditions. Study group The study included four academy groups: U15, U16, U17, and U19, with a total of 59 athletes participating. According to the post-hoc power analysis conducted using G*Power, the moderation analysis performed with 59 participants yielded a statistical power of 83.2% under the assumption of a medium effect size (f² = 0.15), a significance level of 5%, and three predictors (independent variable, moderator, and interaction term) (Noncentrality parameter λ = 8.85; Critical F = 4.02). These results indicate that the sample size provided adequate statistical power to test the moderation effect. Inclusion Criteria: Absence of acute or chronic pain in the lower extremities, No lower extremity injury within the past 6 months, Possession of a valid soccer license, At least 3 years of active soccer experience, Participation in at least 3 training sessions per week. General test procedure The athletes were informed about the purpose, importance, and content of the tests, instructed to refrain from physical activity beforehand, and asked to wear shorts and a T-shirt. All measurements were conducted in the performance laboratory between 15:00 and 17:00. Prior to testing, height and body mass measurements were obtained, and the athletes’ dominant and non-dominant sides were recorded on the assessment form. Subsequently, the athletes performed a 5-minute warm-up exercise on a cycle ergometer; following this, physical measurements were conducted first, followed by motor performance tests. Muscle strength measurement protocol Muscle strength measurements were performed using a manual dynamometer (ActivForce 2, ActivForce, USA). Pino-Ortega et al. [ 13 ] reported that the ActivForce dynamometer demonstrates high reliability in muscle strength assessments (ICC = 0.913–0.930; Cronbach’s Alpha = 0.920–0.938). Prior to the measurements, in order to familiarize the athletes with the test, a total of four submaximal isometric contractions targeting the quadriceps and hamstring muscle groups were performed on the dominant leg (DL); these trials were not recorded. Subsequently, four maximal isometric contractions were measured for each muscle group. To prevent muscle fatigue, a one-minute rest interval was provided between each trial. For quadriceps muscle strength measurement, the athletes were positioned in a seated posture on an examination table, and the knee extension angle was fixed at 60° using a strap placed at knee level. The dynamometer was positioned on the anterior surface of the lower leg, over the tibia, approximately 5 cm above the lateral malleolus. The athletes were instructed to perform a maximal isometric contraction for at least 5 seconds by extending their knee [ 14 ]. For hamstring muscle strength measurement, the athletes were positioned in a seated posture on the examination table, and the dynamometer was externally stabilized with a safety strap placed 1 cm proximal to the midpoint of the Achilles tendon. The athletes were instructed to perform a maximal isometric contraction for at least 5 seconds to produce knee flexion [ 15 ]. In all measurements, the highest peak isometric muscle strength was recorded in kilograms (kg). Trials in which the athletes were unable to sustain the 5-second contraction were considered invalid and repeated. Range of motion measurement protocol All measurements were performed using a manual goniometer (Lafayette Instrument Company, USA). The manufacturer reports that this device provides high measurement reliability (ICC = 0.85–0.99) with an accuracy of 1° for angles up to 180° [ 16 ]. During ROM measurements, athletes were instructed to remain relaxed and to achieve maximal angles during active movement. Each measurement was repeated three times on the dominant leg, and the average of these measurements was used for analysis. All assessments were conducted by the same researcher, and a standardized protocol was followed to minimize intra-rater variability. For knee flexion ROM measurement, athletes were positioned supine with the knees fully extended. The center of the goniometer was placed over the knee joint; the stationary arm was aligned along the femur, and the movable arm along the tibia. Following alignment, the athlete was instructed to actively flex the knee and draw the heel toward the gluteal region [ 17 ]. For hip flexion ROM measurement, athletes were evaluated in the supine position with the knees slightly flexed. The goniometer was positioned at the center of the hip joint; the stationary arm was aligned along the trunk, and the movable arm along the femur. The athlete was then instructed to actively draw the thigh toward the abdomen [ 17 ]. For hip extension ROM measurement, athletes were positioned prone. The center of the goniometer was placed over the hip joint; the stationary arm was aligned with the trunk axis, and the movable arm with the femur axis. The athlete was instructed to actively extend the hip by lifting the thigh upward from the ground [ 17 ]. Reactive strength index and vertical jump height measurement protocol The drop jump test was administered on the dominant leg using the Jump Mat Pro (FSL Electronics, Northern Ireland). The reported reliability coefficient of the device for drop jump measurement is 0.64 [ 18 ]. Athletes stepped off a 30 cm platform onto the electronic mat with one foot and performed a maximal vertical jump with minimal ground contact time, with arms free. Trials were considered invalid and repeated if the knee was excessively flexed upward during the jump or if the landing occurred outside the mat. The test was performed twice with two-minute rest intervals, and RSI (m/s) and jump height data were recorded [ 18 ]. Standing long jump test protocol Horizontal jump performance was evaluated using a single-leg horizontal jump test performed with the dominant leg. A line 0.3 m in width was used as the starting point, and a measuring tape 6 meters in length and 20 cm in width extending from the midpoint of the line was placed on the ground. During the test, athletes stood on the dominant foot at the marked starting line, jumped forward as far as possible with the same foot, and landed on the same foot. The test was repeated twice for each athlete, and the most successful attempt—measured in centimeters between the starting line and the heel—was recorded. As a criterion for a successful trial, athletes were required to achieve full stabilization upon landing and maintain balance for three seconds [ 19 ]. Data Analysis To determine the required minimum sample size, a power analysis was conducted using G*Power 3.1 (Universität Düsseldorf: Psychologie-HHU). Statistical analyses of the obtained data were performed using IBM SPSS Statistics (IBM). Prior to analysis, basic assumptions were tested [ 20 ]. The normality of residuals was assessed using the Shapiro–Wilk test, and p > 0.05 was obtained for all variables. Linearity was examined through scatterplots between dependent and independent variables, and linear relationships were observed. The assumption of homogeneity of variances (homoscedasticity) was evaluated using residuals versus observed values plots, which indicated random distribution of residuals. Autocorrelation was assessed using the Durbin–Watson test, yielding values ranging between 1.83 and 2.10, which were determined to fall within acceptable limits [ 21 ]. Based on these assumptions, it was concluded that Moderated Regression Analysis was applicable. Accordingly, to test the moderating role of age in the relationship between lower extremity physical characteristics and motor performance, version 4.2 of the PROCESS macro developed by Hayes (Model 1) was employed. In the analyses, bootstrap resampling with 5000 iterations was used to generate estimates within a 95% confidence interval, and interaction terms were evaluated for statistical significance. For significant interactions, simple slope analyses and the Johnson–Neyman procedure were conducted to determine the direction of the interaction and the age levels at which the effect was significant. In all statistical tests, the significance level was set at p < 0.05. Results Table 1 The role of age in the effect of ROM and muscle strength parameters on RSI performance Predictor (Predicted = RSI) B SE p LLCI ULCI R 2 / R 2 Change F p ROM*Age*RSI Hip Flexion ROM (cm) 0.064 0.029 0.030* 0.006 0.121 0.196 6.096 0.001** Age 0.432 0.234 0.069 -0.035 0.899 Hip Flexion ROM × Age Interaction -0.003 0.002 0.060 -0.007 0.000 0.039 3.641 0.060 Hip Extension ROM (cm) 0.113 0.038 0.004** 0.037 0.189 0.216 6.870 0.000** Age 0.235 0.100 0.021* 0.037 0.434 Hip Extension ROM × Age Interaction -0.006 0.002 0.008** -0.010 -0.002 0.076 7.308 0.008* Knee Flexion ROM (cm) 0.181 0.052 0.001** 0.078 0.234 0.239 7.852 0.000** Age 1.316 0.412 0.002** 0.496 2.137 Knee Flexion ROM × Age Interaction -0.010 0.003 0.002** -0.016 -0.004 0.107 10.550 0.002** Strength*Age*RSI Quadriceps Strength (kg) 0.077 0.035 0.031* 0.007 0.146 0.207 6.537 0.001** Age 0.114 0.077 0.144 -0.040 0.269 Quadriceps Strength × Age Interaction -0.004 0.002 0.063 -0.008 0.000 0.038 3.567 0.063 Hamstring Strength (kg) 0.106 0.055 0.057 -0.003 0.214 0.201 6.277 0.001** Age 0.059 0.062 0.348 -0.065 0.183 Hamstring Strength × Age Interaction -0.005 0.003 0.115 -0.011 0.001 0.027 2.547 0.115 Significance level (bold) *p < 0.05, **p < 0.01, CM Centimeter, KG Kilogram, ROM Range of motion, SE Standard error, LLCI Lower limit of the confidence interval, ULCI Upper limit of the confidence interval Table 1 shows the multiple regression analyses that examined the effects of age-related interactions between lower extremity ROM and muscle strength variables on RSI, yielding significant models. Hip flexion ROM demonstrated a significant and positive effect on RSI (B = 0.064, p = 0.030). However, the main effect of age (p = 0.069) and the hip flexion ROM × age interaction (p = 0.060) were not statistically significant. The overall explanatory power of the model was moderate and significant (R² = 0.196; F = 6.096; p = 0.001). Although the inclusion of the interaction term with age resulted in a 3.9% increase in explained variance, this contribution was not statistically significant (R² change = 0.039; p = 0.060). The Johnson–Neyman test indicated that this relationship was significant only in soccer players under 17.82 years of age and lost significance above this age threshold. Hip extension ROM, age, and the interaction term were all statistically significant (B = 0.113, p = 0.004; B = 0.235, p = 0.021; B = − 0.006, p = 0.008). The overall explanatory power of the model was moderate and significant (R² = 0.216; F = 6.870; p = 0.000). The inclusion of the interaction term led to a significant 7.6% increase in explained variance (R² change = 0.076; p = 0.008). The Johnson–Neyman test revealed that this relationship was significant only in players under 17.76 years of age and became non-significant above this threshold. Knee flexion ROM, age, and the interaction term were all statistically significant (B = 0.181, p = 0.001; B = 1.316, p = 0.002; B = − 0.010, p = 0.002). The model demonstrated moderate and significant explanatory power (R² = 0.239; F = 7.852; p = 0.000). The addition of the interaction term resulted in a significant 10.7% increase in explained variance (R² change = 0.107; p = 0.002). The Johnson–Neyman analysis indicated that this association was significant only in soccer players under 17.69 years of age. Quadriceps muscle strength showed a significant positive effect on RSI (B = 0.077, p = 0.031). However, the main effect of age (p = 0.144) and the quadriceps strength × age interaction (p = 0.063) were not statistically significant. The overall model was moderate and significant (R² = 0.207; F = 6.537; p = 0.001). Although the interaction term increased the explained variance by 3.8%, this increase was not statistically significant (R² change = 0.038; p = 0.063). The Johnson–Neyman test indicated that the relationship was significant only in players under 17.62 years of age. Hamstring muscle strength, age, and their interaction were not statistically significant predictors (p > 0.05). Nevertheless, the overall model was moderate and significant (R² = 0.201; F = 6.277; p = 0.001). The inclusion of the interaction term led to a 2.7% increase in explained variance, which was not statistically significant (R² change = 0.027; p = 0.115). The Johnson–Neyman analysis showed that the relationship was significant only in players under 18.23 years of age. Table 2 The role of age in the effect of ROM and muscle strength parameters on vertical jump performance Predictor (Predicted=Vertical Jump) B SE p LLCI ULCI R 2 / R 2 Change F p ROM*Age*Vertical Jump Hip Flexion ROM (cm) 2.581 0.713 0.001** 1.161 4.002 0.340 12.872 0.000** Age 20.533 5.802 0.001** 8.975 32.091 Hip Flexion ROM × Age Interaction -0.139 0.042 0.001** -0.222 -0.055 0.096 10.907 0.001** Hip Extension ROM (cm) 3.223 0.961 0.001** 1.309 5.136 0.327 12.155 0.000** Age 8.549 2.519 0.001** 3.532 13.566 Hip Extension ROM × Age Interaction -0.170 0.056 0.003** -0.281 -0.059 0.083 9.279 0.003** Knee Flexion ROM (cm) 6.513 1.143 0.000** 4.235 8.790 0.500 24.963 0.000** Age 49.259 9.120 0.000** 31.090 67.427 Knee Flexion ROM × Age Interaction -0.349 0.066 0.000** -0.481 -0.217 0.185 27.729 0.000** Strength*Age*Vertical Jump Quadriceps Strength (kg) 3.291 0.766 0.000** 1.764 4.817 0.488 23.786 0.000** Age 7.236 1.702 0.000** 3.845 10.626 Quadriceps Strength × Age Interaction -0.173 0.046 0.000** -0.264 -0.082 0.098 14.279 0.000** Hamstring Strength (kg) 4.792 1.328 0.001** 2.146 7.437 0.366 14.434 0.000 Age 5.517 1.517 0.001** 2.495 8.539 Hamstring Strength × Age Interaction -0.250 0.078 0.002** -0.405 -0.096 0.088 10.388 0.002** Significance level (bold) **p < 0.01, CM Centimeter, KG Kilogram, ROM Range of motion, SE Standard error, LLCI Lower limit of the confidence interval, ULCI Upper limit of the confidence interval Table 2 shows that all models were found to be statistically significant as a result of multiple regression analyses regarding the effects of age-related interactions of lower extremity ROM and muscle strength variables on vertical jump performance. For hip flexion ROM, age, and the interaction term were all significant (B = 2.581, p = 0.001; B = 20.533, p = 0.001; B = − 0.139, p = 0.001). The model demonstrated high and significant explanatory power (R² = 0.340; F = 12.872; p = 0.000). The inclusion of the interaction term resulted in a significant 9.6% increase in explained variance (R² change = 0.096; p = 0.001). The Johnson–Neyman test indicated significance only in players under 17.60 years of age. For hip extension ROM, age, and the interaction term were again significant (B = 3.223, p = 0.001; B = 8.549, p = 0.001; B = − 0.170, p = 0.003). The model exhibited high explanatory power (R² = 0.327; F = 12.155; p = 0.000), with an 8.3% significant increase in explained variance after adding the interaction term (R² change = 0.083; p = 0.003). Significance was observed only below 17.85 years of age. For knee flexion ROM, both main effects and the interaction term were significant (B = 6.513, p = 0.000; B = 49.259, p = 0.000; B = − 0.349, p = 0.000). The model demonstrated high explanatory power (R² = 0.500; F = 24.963; p = 0.000), and the interaction term contributed a significant 18.5% increase in explained variance (R² change = 0.185; p = 0.000). The Johnson–Neyman analysis indicated significance below 18.02 years of age. Similarly, in the quadriceps strength model, both main effects and the interaction term were significant (B = 3.291, p = 0.000; B = 7.236, p = 0.000; B = − 0.173, p = 0.000). The model showed high explanatory power (R² = 0.488; F = 23.786; p = 0.000), with a significant 9.8% increase in explained variance due to the interaction term (R² change = 0.098; p = 0.000). Significance was limited to players under 17.98 years of age. For hamstring strength, both main effects and the interaction term were also significant (B = 4.792, p = 0.001; B = 5.517, p = 0.001; B = − 0.250, p = 0.002). The model demonstrated high explanatory power (R² = 0.366; F = 14.434; p = 0.000), with an 8.8% significant increase in explained variance (R² change = 0.088; p = 0.002). The Johnson–Neyman test indicated significance only in players under 17.99 years of age. Table 3 The role of age in the effect of ROM and muscle strength parameters on horizontal jump performance Predictor (Predicted=Horizontal Jump) B SE p LLCI ULCI R 2 / R 2 Change F p ROM*Age*Horizontal Jump Distance Hip Flexion ROM (cm) 12.558 6.103 0.043* 0.400 24.716 0.445 20.005 0.000** Age 66.222 49.658 0.186 -32.701 165.146 Hip Flexion ROM × Age Interaction -0.591 0.360 0.104 -1.308 0.125 0.020 2.702 0.104 Hip Extension ROM (cm) 30.991 8.054 0.000** 14.947 47.035 0.457 21.019 0.000** Age 54.108 21.115 0.012* 12.045 96.171 Hip Extension ROM × Age Interaction -1.651 0.468 0.001** -2.584 -0.718 0.090 12.427 0.001** Knee Flexion ROM (cm) 37.761 10.892 0.001** 16.064 59.458 0.478 22.918 0.000** Age 250.909 86.893 0.005** 77.809 424.010 Knee Flexion ROM × Age Interaction -1.948 0.632 0.003** -3.206 -0.689 0.066 9.509 0.003** Strength*Age*Horizontal Jump Distance Quadriceps Strength (kg) 24.852 6.678 0.000** 11.548 38.155 0.553 30.918 0.000** Age 26.809 14.833 0.075 -2.741 56.358 Quadriceps Strength × Age Interaction -1.280 0.399 0.002** -2.075 -0.484 0.061 10.264 0.002** Hamstring Strength (kg) 42.144 11.365 0.000** 19.503 64.785 0.466 21.860 0.000** Age 20.874 12.986 0.112 -4.996 46.743 Hamstring Strength × Age Interaction -2.211 0.665 0.001** -3.535 -0.886 0.079 11.057 0.001** Significance level (bold) *p < 0.05, **p < 0.01, CM Centimeter, KG Kilogram, ROM Range of motion, SE Standard error, LLCI Lower limit of the confidence interval, ULCI Upper limit of the confidence interval Table 3 shows the results of multiple regression analyses examining the effects of age-related interactions between lower extremity ROM and muscle strength variables on horizontal jump performance, revealing statistically significant differences in some variables. Hip flexion ROM showed a significant and positive effect on horizontal jump performance (B = 12.558, p = 0.043). However, the main effect of age (p = 0.186) and the hip flexion ROM × age interaction (p = 0.104) were not significant. The model demonstrated high and significant explanatory power (R² = 0.445; F = 20.005; p = 0.000). Although the interaction term led to a 2% increase in explained variance, this contribution was not statistically significant (R² change = 0.020; p = 0.104). The Johnson–Neyman test indicated significance only below 18.54 years of age. For hip extension ROM, age and the interaction term were significant (B = 30.991, p = 0.000; B = 54.108, p = 0.012; B = − 1.651, p = 0.001). The model exhibited high explanatory power (R² = 0.457; F = 21.019; p = 0.000), with a significant 9% increase in explained variance (R² change = 0.090; p = 0.001). Significance was limited to players under 17.84 years of age. For knee flexion ROM, all main effects and the interaction term were significant (B = 37.761, p = 0.001; B = 250.909, p = 0.005; B = − 1.948, p = 0.003). The model demonstrated high explanatory power (R² = 0.478; F = 22.918; p = 0.000), with a significant 6.6% increase in explained variance (R² change = 0.066; p = 0.003). The Johnson–Neyman analysis indicated significance below 18.23 years of age. Quadriceps strength significantly and positively affected horizontal jump performance (B = 24.852, p = 0.000). The interaction term was also significant (B = − 1.280, p = 0.002), whereas the individual effect of age was not (p = 0.075). The model showed high explanatory power (R² = 0.553; F = 30.918; p = 0.000), with a significant 6.1% increase in explained variance (R² change = 0.061; p = 0.002). The Johnson–Neyman test indicated significance only in players under 18.14 years of age. Similarly, hamstring strength was a significant predictor (B = 42.144, p = 0.000). Although the interaction term was significant (B = − 2.211, p = 0.001), the individual effect of age was not statistically significant (p = 0.112). The model demonstrated high explanatory power (R² = 0.466; F = 21.860; p = 0.000), with a significant 7.9% increase in explained variance (R² change = 0.079; p = 0.001). The Johnson–Neyman analysis revealed that the relationship was significant only in players under 17.96 years of age. Discussion The present study examined the effects of lower extremity ROM and muscle strength on motor performance, with a particular focus on the moderating role of age. Overall, the results indicate that these relationships are age-dependent, with stronger effects observed in younger athletes. In the first result of our study, the effects of ROM and muscle strength variables on RSI were evaluated in interaction with the age factor. In terms of ROM parameters, hip flexion, hip extension, and knee flexion ranges of motion demonstrated significant predictive effects on RSI in interaction with age. The significance of the interaction terms across all three variables indicates that the influence of these ranges of motion on RSI varies depending on age. These results suggest that hip joint mobility, in particular, is more effective during the transition from the amortization phase to the take-off phase, enhancing the efficiency of the stretch–shortening cycle and thereby supporting RSI performance. According to the Johnson–Neyman analyses, the fact that these effects were significant particularly in athletes under 17–18 years of age suggests that, developmentally, joint mobility is more determinant for reactive performance at younger ages. The incomplete maturation of neuromuscular coordination during these years may increase the contribution of range of motion to performance [ 22 ]. However, with increasing age, the influence of mobility on agility-based outcomes such as RSI appears to diminish, being replaced by strength, speed, and synchronized muscle activation [ 12 ]. With regard to strength variables, quadriceps muscle strength significantly and positively predicted RSI, whereas hamstring muscle strength did not demonstrate a significant effect. Although the interaction with age was not significant for quadriceps strength, the relationship appeared more pronounced in the younger age groups. This result may be attributed to the quadriceps muscles serving as the primary propulsive power during RSI tasks [ 23 ]. In contrast, the supportive role of the hamstring muscles may not be sufficient to independently explain RSI performance [ 24 ]. Furthermore, age-related improvements in the direction, timing, and coordination of strength production appear to enhance the contribution of the quadriceps muscles to performance, whereas this effect seems more limited at younger ages [ 25 ]. In the second result of our study, the effects of ROM and muscle strength variables on vertical jump performance were evaluated in interaction with age. In terms of ROM parameters, the significance of both the main effects and the age interactions for hip flexion, hip extension, and knee flexion ROM indicates that the contribution of these parameters to vertical jump performance varies according to age. The fact that these effects were significant particularly in individuals under 17–18 years of age suggests that joint range of motion is more determinant for jump performance during developmental stages. In this age group, as synchronized motor unit recruitment, explosive power production, and coordination are not yet fully developed, joint mobility may provide a compensatory advantage [ 26 ]. However, the disappearance of these effects with increasing age suggests that, in complex motor outputs such as jumping, ROM is progressively replaced by greater contributions from strength, speed, and neuromuscular control [ 26 ]. Regarding strength parameters, the significant interactions of both quadriceps and hamstring muscle strength with age indicate that the influence of muscle strength on vertical jump performance also differs according to age. Since the quadriceps muscle acts as the primary extensor during jumping, increases in strength at younger ages may significantly enhance jump height. However, with advancing age and the development of technical proficiency as well as intra- and inter-muscular coordination, the direct impact of strength on performance appears to weaken [ 24 ]. Similarly, the relationship that was significant for hamstring strength at younger ages lost its significance with increasing age. This may be explained by the supportive role of the hamstring muscles during jumping, as their contribution is more related to control, stabilization, and the landing phase [ 24 ]. Overall, both ROM and muscle strength variables appear to exert age-sensitive effects on jump performance, with their influence diminishing or being replaced by other motor factors as part of the developmental process. In the third result of our study, the effects of ROM and muscle strength variables on horizontal jump performance were evaluated in interaction with the age factor. In terms of ROM parameters, hip extension and knee flexion ROM were found to influence horizontal jump performance at different levels depending on age. The fact that these ranges of motion were significant predictors particularly in individuals under 17–18 years of age suggests that joint mobility plays a greater role during the wide propulsion angle and prolonged acceleration phase required in horizontal jumping. Since strength production time is longer in younger age groups, a greater range of motion may support this process and increase jump distance [ 27 ]. However, with increasing age, propulsion time shortens and movement efficiency improves, relatively reducing the effect of ROM. Although hip flexion ROM did not demonstrate a significant interaction with age, it was found to be significant in individuals under 18 years of age. This result suggests that hip flexion may provide an advantage for younger athletes during the forward trunk flexion and loading phase required for horizontal jumping [ 27 ]. Regarding muscle strength variables, the age-dependent effects observed for both quadriceps and hamstring strength indicate that the role of strength in horizontal jump performance changes throughout the developmental process. Particularly at younger ages, insufficient integration of muscle strength with technical control may cause strength to be reflected more directly in performance [ 28 ]. This may explain why quadriceps strength emerged as a significant determinant in athletes under 18 years of age. Similarly, the fact that hamstring strength was significant only in the younger age group may be attributed to the role of these muscles in maintaining the balance between hip extension and knee flexion during jumping, thereby contributing to propulsion efficiency. However, with increasing age and improved movement economy, this contribution becomes less critical [ 28 ]. Overall, the effects of ROM and muscle strength variables on horizontal jump performance appear to vary according to age; these physical characteristics exert a more direct influence at younger ages, whereas technical proficiency and movement strategies become more prominent with advancing age. These results are consistent with the literature reporting age-related effects of lower extremity mobility and muscle strength on motor performance. For example, it has been reported that during adolescence, the stretch–shortening cycle improves significantly with the development of the neuromuscular system, with quadriceps muscle strength and lower extremity flexibility playing a determinant role in this improvement [ 9 , 10 , 22 ]. Although both quadriceps and hamstring strength increase with age, muscle imbalances between these groups are frequently observed in younger age groups (particularly 12–16 years), which may contribute to performance limitations and inefficient functioning of the stretch–shortening cycle [ 23 , 25 ]. Furthermore, the contribution of hip and knee ROM to reactive jump performance provides a more pronounced advantage in age groups where neuromuscular coordination has not yet fully matured [ 12 , 29 ]. Similarly, vertical jump performance has been shown to be age-sensitive; during the prepubertal period, insufficient elastic energy reutilization limits performance, whereas in adolescence, improvements in muscle–tendon structure and neuromuscular coordination result in marked performance enhancements [ 11 ]. In young adulthood, maximal strength production and explosive power capacity further elevate this development to its highest level [ 11 ]. On the other hand, it has been reported that during adolescence, hip and knee joint range of motion may exert a more pronounced influence on explosive jump outcomes than strength or neuromuscular proficiency [ 26 ]. In particular, in the 12–16 age group, the contribution of such mobility to performance becomes more evident [ 26 ]. Additionally, in motor skills such as horizontal jumping, which require a wide propulsion angle and prolonged acceleration, the importance of specific ROM values such as hip extension and knee flexion has been emphasized. It has also been reported that age-related increases in joint mobility positively affect horizontal jump performance in young female athletes [ 27 ]. Moreover, it has been suggested that evaluating muscle strength balance and mobility together enables more accurate prediction of jump performance in young athletes [ 28 ]. In this context, the age-dependent interaction effects identified in our study are grounded in a biomechanically and developmentally meaningful framework in light of the existing literature. Limitations This study has several limitations. The inclusion of only elite male soccer players limits the generalizability of the results to different sexes and sports disciplines. Due to its cross-sectional design, the study does not allow for causal inferences. Age groups were classified according to chronological age rather than biological maturation, which may have overlooked individual developmental differences. Additionally, psychological and environmental factors such as sleep, fatigue, and motivation were not controlled. These limitations should be taken into consideration when interpreting the results. Conclusion This research revealed that the effects of lower extremity range of motion and muscle strength variables on motor performance differ significantly according to age. In particular, the more pronounced effects of physical parameters on both RSI and jump performance in individuals under 17–18 years of age indicate that range of motion and muscle strength are more directly reflected in motor outputs within this age group. However, with increasing age, the influence of these variables decreases, and motor performance becomes more dependent on complex processes such as the direction and timing of strength production and neuromuscular control. The result that broader age-range groups served as significant predictors particularly in horizontal jump performance suggests that this motor skill more clearly reflects age-related development. In contrast, the absence of age as an independent determinant in tasks such as RSI and vertical jump indicates that age assumes an indirect role, operating only in interaction with physical characteristics. Accordingly, the development of motor performance appears to be associated not merely with advancing age, but with the extent to which age-specific physical capacities are functionally optimized. Therefore, training programs should consider developmental characteristics specific to each age group. In particular, in U15–U17 groups, maintaining ROM capacity and emphasizing multidirectional strength development (such as eccentric strength training, isokinetic exercises, and plyometric preparation) should be prioritized, while technical skill acquisition should be progressively integrated in parallel with the development of neuromuscular control. Abbreviations CM Centimeter DL Dominant leg ICC Intraclass correlation coefficients KG Kilograms LLCI Lower limit of the confidence interval ROM Range of motion RSI Reactive strength index SE Standard error ULCI Upper limit of the confidence interval Declarations Acknowledgements The authors would like to express their sincere gratitude to the Recep Tayyip Erdoğan University Development Foundation for their financial support. The authors also thank all participants for their valuable contribution to the study. Author contributions All authors contributed to the design and planning of the study. Data collection, analysis, and interpretation were performed by H.İ.Ç., R.F.K., E.T. and H.K. The first draft of the manuscript was written by E.T. and previous versions were reviewed by all authors. All authors read and approved the final version of the manuscript. Funding statement This study has been supported by the Recep Tayyip Erdoğan University Development Foundation (Grant number: 02026004007238). Data availability statement The datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request. Ethics approval and consent to participate This cross-sectional study was approved by the Ethics Committee of the Faculty of Social and Human Sciences at Recep Tayyip Erdogan University (Date: 18/02/2026; Approval No: 2026/75). All procedures were conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants and their legal guardians, and permission was secured from the affiliated sports club prior to data collection. All relevant documents were submitted for ethical review in advance. Consent for publication Not applicable. Competing interests The authors declare no competing interests. References Turner AN, Stewart PF. 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The influence of growth and maturation on stretch-shortening cycle function in youth. Sports Med. 2018;48:57–71. https://doi.org/10.1007/s40279-017-0785-0 . Mandroukas A, Michailidis Y, Metaxas T. Muscle strength and hamstrings to quadriceps ratio in young soccer players: A cross-sectional study. J Funct Morphol Kinesiol. 2023;8(2):70. https://doi.org/10.3390/jfmk8020070 . França C, Saldanha C, Martins F, Nascimento M, Marques A, Ihle A, et al. Lower body strength and body composition in female football. Sci Rep. 2025;15(1):9200. https://doi.org/10.1038/s41598-025-94041-x . Peek K, Gatherer D, Bennett KJ, Fransen J, Watsford M. Muscle strength characteristics of the hamstrings and quadriceps in players from a high-level youth football (soccer) Academy. Res Sports Med. 2018;26(3):276–88. https://doi.org/10.1080/15438627.2018.1447475 . Cejudo A, Robles-Palazón FJ, Ayala F, Croix MDS, Ortega-Toro E, Santonja-Medina F, et al. Age-related differences in flexibility in soccer players 8–19 years old. PeerJ. 2019;7:e6236. http://dx.doi.org/10.7717/peerj.6236 . Fältström A, Skillgate E, Tranaeus U, Weiss N, Källberg H, Lyberg V, et al. Normative values and changes in range of motion, strength, and functional performance over 1 year in adolescent female football players: Data from 418 players in the Karolinska football injury cohort study. Phys Ther Sport. 2022;58:106–16. https://doi.org/10.1016/j.ptsp.2022.10.003 . Babakhani F, Hatefi M, Balochi R. Is there a relationship between isometric hamstrings-to-quadriceps torque ratio and athletes’ plyometric performance? PLoS ONE. 2023;18(11):e0294274. https://doi.org/10.1371/journal.pone.0294274 . Sugimoto D, Borg DR, Brilliant AN, Meehan WP III, Micheli LJ, Geminiani ET. Effect of sports and growth on hamstrings and quadriceps development in young female athletes: Cross-sectional study. Sports. 2019;7(7):158. https://doi.org/10.3390/sports7070158 . 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9372764","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":623392482,"identity":"fc6890e6-fa7e-445d-addf-41bd46ae9485","order_by":0,"name":"Halil İbrahim Çakır","email":"","orcid":"","institution":"Recep Tayyip Erdogan University","correspondingAuthor":false,"prefix":"","firstName":"Halil","middleName":"İbrahim","lastName":"Çakır","suffix":""},{"id":623392483,"identity":"5a3d0aea-592f-476b-8394-4e9f0dc0ce00","order_by":1,"name":"Recep Fatih Kayhan","email":"","orcid":"","institution":"Marmara University","correspondingAuthor":false,"prefix":"","firstName":"Recep","middleName":"Fatih","lastName":"Kayhan","suffix":""},{"id":623392484,"identity":"ea8afd7e-b953-4d8f-8526-0fdd25478e41","order_by":2,"name":"Esranur Terzi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA50lEQVRIiWNgGAWjYHADxsbHYJqZuYEo9RJALc3GDAwGQC2MRGthYJMGa2EgoIWf/+zDz4Vt9+rM+w+3VRdU/Inmbwdq+VGxDacWyRnpxtIz24olZA4cbLs944xB7ozDjA2MPWdu49RicIONQZq3LUFCgrGx7TZvm0FuA1ALM2Mbbi32548x/wZrASorBmmZT0iLAUMaG8QWNsY2ZpCWDYS0SNxIY7PmOZcgOYOHsVma54xx7kagloP4/MLff4z5Nk9ZAr8E//GHn3kq5HLnnT988MGPCtxasIMDJKofBaNgFIyCUYAGAEFaTuPytKEyAAAAAElFTkSuQmCC","orcid":"","institution":"Recep Tayyip Erdogan University","correspondingAuthor":true,"prefix":"","firstName":"Esranur","middleName":"","lastName":"Terzi","suffix":""},{"id":623392485,"identity":"6c5777e6-555d-4d92-8fe0-553782941e16","order_by":3,"name":"Harun Koç","email":"","orcid":"","institution":"Dumlupinar University","correspondingAuthor":false,"prefix":"","firstName":"Harun","middleName":"","lastName":"Koç","suffix":""}],"badges":[],"createdAt":"2026-04-09 22:53:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9372764/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9372764/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107706222,"identity":"e7944275-ed30-428d-afef-9520c2b9cea4","added_by":"auto","created_at":"2026-04-24 09:17:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":491504,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9372764/v1/53608df7-0077-4abe-8a03-d0293d695f03.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The moderating role of age in the effect of hip and knee joint functions on explosive power performance in soccer players","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSoccer is a multidimensional sport in which anaerobic power, agility, balance, and a high level of neuromuscular coordination function collectively. By its very nature, the structure of the game involves short-duration, high-intensity efforts such as rapid changes of direction, sudden accelerations, jumping, and leaping. These performance demands cause the physical and neuromuscular characteristics of the lower extremities to play a decisive role in athletic success [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWithin this framework, muscle strength\u0026mdash;one of the key determinants of motor performance\u0026mdash;emerges as a parameter subject to developmental changes with age [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In particular, the strength levels of the quadriceps and hamstring muscle groups play a critical role in performing high-intensity movements such as running, jumping, and change of direction in soccer players [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The strength capacity of these muscles is directly related to the effectiveness of eccentric and concentric contractions, as well as to the functionality of the stretch-shortening cycle [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In this context, the Reactive Strength Index (RSI) provides information about the duration and magnitude of power applied to the ground by utilizing the elastic properties of the muscle\u0026ndash;tendon complex [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In this respect, RSI serves as a neuromechanical output of lower extremity strength and is a valuable indicator in predicting both vertical and horizontal jump performance [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. While vertical jump assesses explosive power and the capacity to generate power against gravity, horizontal jump is an effective tool for evaluating forward power production and dynamic balance capacity [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Accordingly, the inclusion of both vertical and horizontal jump tests in our study enables the assessment of the multidirectional power production capacity of the lower extremities. In addition to muscle strength, joint range of motion (ROM) is another important determinant of motor performance [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Adequate ROM allows body segments to operate within optimal movement amplitudes, thereby contributing to the more efficient and controlled execution of motor tasks. Insufficient ROM, on the other hand, may lead to the development of compensatory strategies during movement, resulting in both performance decrements and an increased risk of injury. In particular, adequate range of motion in the hip and knee joints enables the kinetic chain to function effectively and synchronously during tasks such as sprinting, jumping, and changing direction [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOne of the environmental and biological factors influencing the development of these physical characteristics is age. Neuromuscular changes occurring during adolescence lead to developmental differences in both muscle strength and motor control mechanisms, varying in rate and manner [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In this context, age groups (e.g., U15, U16, U17, U19) are likely to play a moderating role in the relationships between physical characteristics and motor performance. Although age-based analyses of this nature have been reported in the literature [\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], studies that simultaneously address multiple physical characteristics such as ROM and muscle strength and test the effect of age on these relationships using multivariate models are limited [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The present study not only compares age groups in terms of motor performance but also provides a multivariate perspective by considering age together with physical variables such as ROM and strength. That is, in our research, age was examined within a framework in which performance was modeled and analyzed alongside other physical determinants. In this regard, the study presents an original structure that evaluates the developmental effects of physical characteristics in conjunction with age. From this perspective, the study has the potential to make significant contributions to subfields of sport sciences such as developmental physiology, performance analysis, and training planning.\u003c/p\u003e \u003cp\u003eAccordingly, the aim of the present study is to examine, through multivariate models, the effects of lower extremity physical characteristics (muscle strength and joint range of motion) on motor performance indicators (RSI, vertical jump, and horizontal jump) in soccer players from different age groups and to reveal the moderating role of age in these relationships. In line with this objective, it was hypothesized that (i) age significantly affects the relationship between ROM and motor performance, and (ii) age significantly affects the relationship between muscle strength and motor performance.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design\u003c/h2\u003e \u003cp\u003eThis study was structured within a cross-sectional, regression-based moderation framework to elucidate the role of age in shaping the relationship between lower extremity physical attributes (muscle strength and joint ROM) and motor performance outcomes (RSI, vertical and horizontal jump) in youth soccer players. By integrating interaction terms into multivariate models, the design enabled a comprehensive evaluation of age-related differential effects under standardized laboratory conditions.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStudy group\u003c/h3\u003e\n\u003cp\u003eThe study included four academy groups: U15, U16, U17, and U19, with a total of 59 athletes participating. According to the post-hoc power analysis conducted using G*Power, the moderation analysis performed with 59 participants yielded a statistical power of 83.2% under the assumption of a medium effect size (f\u0026sup2; = 0.15), a significance level of 5%, and three predictors (independent variable, moderator, and interaction term) (Noncentrality parameter λ\u0026thinsp;=\u0026thinsp;8.85; Critical F\u0026thinsp;=\u0026thinsp;4.02). These results indicate that the sample size provided adequate statistical power to test the moderation effect.\u003c/p\u003e \u003cp\u003eInclusion Criteria:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eAbsence of acute or chronic pain in the lower extremities,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNo lower extremity injury within the past 6 months,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePossession of a valid soccer license,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAt least 3 years of active soccer experience,\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eParticipation in at least 3 training sessions per week.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e\n\u003ch3\u003eGeneral test procedure\u003c/h3\u003e\n\u003cp\u003eThe athletes were informed about the purpose, importance, and content of the tests, instructed to refrain from physical activity beforehand, and asked to wear shorts and a T-shirt. All measurements were conducted in the performance laboratory between 15:00 and 17:00. Prior to testing, height and body mass measurements were obtained, and the athletes\u0026rsquo; dominant and non-dominant sides were recorded on the assessment form. Subsequently, the athletes performed a 5-minute warm-up exercise on a cycle ergometer; following this, physical measurements were conducted first, followed by motor performance tests.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eMuscle strength measurement protocol\u003c/strong\u003e \u003cp\u003eMuscle strength measurements were performed using a manual dynamometer (ActivForce 2, ActivForce, USA). Pino-Ortega et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] reported that the ActivForce dynamometer demonstrates high reliability in muscle strength assessments (ICC\u0026thinsp;=\u0026thinsp;0.913\u0026ndash;0.930; Cronbach\u0026rsquo;s Alpha\u0026thinsp;=\u0026thinsp;0.920\u0026ndash;0.938). Prior to the measurements, in order to familiarize the athletes with the test, a total of four submaximal isometric contractions targeting the quadriceps and hamstring muscle groups were performed on the dominant leg (DL); these trials were not recorded. Subsequently, four maximal isometric contractions were measured for each muscle group. To prevent muscle fatigue, a one-minute rest interval was provided between each trial. For quadriceps muscle strength measurement, the athletes were positioned in a seated posture on an examination table, and the knee extension angle was fixed at 60\u0026deg; using a strap placed at knee level. The dynamometer was positioned on the anterior surface of the lower leg, over the tibia, approximately 5 cm above the lateral malleolus. The athletes were instructed to perform a maximal isometric contraction for at least 5 seconds by extending their knee [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. For hamstring muscle strength measurement, the athletes were positioned in a seated posture on the examination table, and the dynamometer was externally stabilized with a safety strap placed 1 cm proximal to the midpoint of the Achilles tendon. The athletes were instructed to perform a maximal isometric contraction for at least 5 seconds to produce knee flexion [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In all measurements, the highest peak isometric muscle strength was recorded in kilograms (kg). Trials in which the athletes were unable to sustain the 5-second contraction were considered invalid and repeated.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eRange of motion measurement protocol\u003c/strong\u003e \u003cp\u003eAll measurements were performed using a manual goniometer (Lafayette Instrument Company, USA). The manufacturer reports that this device provides high measurement reliability (ICC\u0026thinsp;=\u0026thinsp;0.85\u0026ndash;0.99) with an accuracy of 1\u0026deg; for angles up to 180\u0026deg; [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. During ROM measurements, athletes were instructed to remain relaxed and to achieve maximal angles during active movement. Each measurement was repeated three times on the dominant leg, and the average of these measurements was used for analysis. All assessments were conducted by the same researcher, and a standardized protocol was followed to minimize intra-rater variability. For knee flexion ROM measurement, athletes were positioned supine with the knees fully extended. The center of the goniometer was placed over the knee joint; the stationary arm was aligned along the femur, and the movable arm along the tibia. Following alignment, the athlete was instructed to actively flex the knee and draw the heel toward the gluteal region [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. For hip flexion ROM measurement, athletes were evaluated in the supine position with the knees slightly flexed. The goniometer was positioned at the center of the hip joint; the stationary arm was aligned along the trunk, and the movable arm along the femur. The athlete was then instructed to actively draw the thigh toward the abdomen [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. For hip extension ROM measurement, athletes were positioned prone. The center of the goniometer was placed over the hip joint; the stationary arm was aligned with the trunk axis, and the movable arm with the femur axis. The athlete was instructed to actively extend the hip by lifting the thigh upward from the ground [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eReactive strength index and vertical jump height measurement protocol\u003c/strong\u003e \u003cp\u003eThe drop jump test was administered on the dominant leg using the Jump Mat Pro (FSL Electronics, Northern Ireland). The reported reliability coefficient of the device for drop jump measurement is 0.64 [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Athletes stepped off a 30 cm platform onto the electronic mat with one foot and performed a maximal vertical jump with minimal ground contact time, with arms free. Trials were considered invalid and repeated if the knee was excessively flexed upward during the jump or if the landing occurred outside the mat. The test was performed twice with two-minute rest intervals, and RSI (m/s) and jump height data were recorded [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eStanding long jump test protocol\u003c/strong\u003e \u003cp\u003eHorizontal jump performance was evaluated using a single-leg horizontal jump test performed with the dominant leg. A line 0.3 m in width was used as the starting point, and a measuring tape 6 meters in length and 20 cm in width extending from the midpoint of the line was placed on the ground. During the test, athletes stood on the dominant foot at the marked starting line, jumped forward as far as possible with the same foot, and landed on the same foot. The test was repeated twice for each athlete, and the most successful attempt\u0026mdash;measured in centimeters between the starting line and the heel\u0026mdash;was recorded. As a criterion for a successful trial, athletes were required to achieve full stabilization upon landing and maintain balance for three seconds [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eData Analysis\u003c/h2\u003e \u003cp\u003eTo determine the required minimum sample size, a power analysis was conducted using G*Power 3.1 (Universit\u0026auml;t D\u0026uuml;sseldorf: Psychologie-HHU). Statistical analyses of the obtained data were performed using IBM SPSS Statistics (IBM).\u003c/p\u003e \u003cp\u003ePrior to analysis, basic assumptions were tested [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The normality of residuals was assessed using the Shapiro\u0026ndash;Wilk test, and p\u0026thinsp;\u0026gt;\u0026thinsp;0.05 was obtained for all variables. Linearity was examined through scatterplots between dependent and independent variables, and linear relationships were observed. The assumption of homogeneity of variances (homoscedasticity) was evaluated using residuals versus observed values plots, which indicated random distribution of residuals. Autocorrelation was assessed using the Durbin\u0026ndash;Watson test, yielding values ranging between 1.83 and 2.10, which were determined to fall within acceptable limits [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Based on these assumptions, it was concluded that Moderated Regression Analysis was applicable.\u003c/p\u003e \u003cp\u003e Accordingly, to test the moderating role of age in the relationship between lower extremity physical characteristics and motor performance, version 4.2 of the PROCESS macro developed by Hayes (Model 1) was employed. In the analyses, bootstrap resampling with 5000 iterations was used to generate estimates within a 95% confidence interval, and interaction terms were evaluated for statistical significance. For significant interactions, simple slope analyses and the Johnson\u0026ndash;Neyman procedure were conducted to determine the direction of the interaction and the age levels at which the effect was significant. In all statistical tests, the significance level was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\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\u003eThe role of age in the effect of ROM and muscle strength parameters on RSI performance\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePredictor (Predicted\u0026thinsp;=\u0026thinsp;RSI)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLLCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eULCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e/\u003c/p\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e Change\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003eROM*Age*RSI\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Flexion ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.064\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.029\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.030*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.121\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.196\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e6.096\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.432\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.234\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.069\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.035\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.899\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Flexion ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.060\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.039\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.641\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.060\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Extension ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.113\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.038\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.004**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.037\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.189\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.216\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e6.870\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.235\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.021*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.037\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.434\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Extension ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.008**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.076\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7.308\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.008*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKnee Flexion ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.052\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.078\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.234\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.239\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e7.852\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.316\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.412\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.002**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.496\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.137\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKnee Flexion ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.002**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.107\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e10.550\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.002**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eStrength*Age*RSI\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuadriceps Strength (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.077\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.035\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.031*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.146\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.207\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e6.537\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.114\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.077\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.144\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.040\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.269\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuadriceps Strength \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.063\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.038\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.567\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.063\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHamstring Strength (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.106\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.057\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.214\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.201\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e6.277\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.059\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.062\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.348\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.065\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.183\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHamstring Strength \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.115\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.547\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.115\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eSignificance level (bold)\u003c/em\u003e *p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, \u003cem\u003eCM\u003c/em\u003e Centimeter, \u003cem\u003eKG\u003c/em\u003e Kilogram, \u003cem\u003eROM\u003c/em\u003e Range of motion, \u003cem\u003eSE\u003c/em\u003e Standard error, \u003cem\u003eLLCI\u003c/em\u003e Lower limit of the confidence interval, \u003cem\u003eULCI\u003c/em\u003e Upper limit of the confidence interval\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the multiple regression analyses that examined the effects of age-related interactions between lower extremity ROM and muscle strength variables on RSI, yielding significant models.\u003c/p\u003e \u003cp\u003eHip flexion ROM demonstrated a significant and positive effect on RSI (B\u0026thinsp;=\u0026thinsp;0.064, p\u0026thinsp;=\u0026thinsp;0.030). However, the main effect of age (p\u0026thinsp;=\u0026thinsp;0.069) and the hip flexion ROM \u0026times; age interaction (p\u0026thinsp;=\u0026thinsp;0.060) were not statistically significant. The overall explanatory power of the model was moderate and significant (R\u0026sup2; = 0.196; F\u0026thinsp;=\u0026thinsp;6.096; p\u0026thinsp;=\u0026thinsp;0.001). Although the inclusion of the interaction term with age resulted in a 3.9% increase in explained variance, this contribution was not statistically significant (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.039; p\u0026thinsp;=\u0026thinsp;0.060). The Johnson\u0026ndash;Neyman test indicated that this relationship was significant only in soccer players under 17.82 years of age and lost significance above this age threshold.\u003c/p\u003e \u003cp\u003eHip extension ROM, age, and the interaction term were all statistically significant (B\u0026thinsp;=\u0026thinsp;0.113, p\u0026thinsp;=\u0026thinsp;0.004; B\u0026thinsp;=\u0026thinsp;0.235, p\u0026thinsp;=\u0026thinsp;0.021; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.006, p\u0026thinsp;=\u0026thinsp;0.008). The overall explanatory power of the model was moderate and significant (R\u0026sup2; = 0.216; F\u0026thinsp;=\u0026thinsp;6.870; p\u0026thinsp;=\u0026thinsp;0.000). The inclusion of the interaction term led to a significant 7.6% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.076; p\u0026thinsp;=\u0026thinsp;0.008). The Johnson\u0026ndash;Neyman test revealed that this relationship was significant only in players under 17.76 years of age and became non-significant above this threshold.\u003c/p\u003e \u003cp\u003eKnee flexion ROM, age, and the interaction term were all statistically significant (B\u0026thinsp;=\u0026thinsp;0.181, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;1.316, p\u0026thinsp;=\u0026thinsp;0.002; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.010, p\u0026thinsp;=\u0026thinsp;0.002). The model demonstrated moderate and significant explanatory power (R\u0026sup2; = 0.239; F\u0026thinsp;=\u0026thinsp;7.852; p\u0026thinsp;=\u0026thinsp;0.000). The addition of the interaction term resulted in a significant 10.7% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.107; p\u0026thinsp;=\u0026thinsp;0.002). The Johnson\u0026ndash;Neyman analysis indicated that this association was significant only in soccer players under 17.69 years of age.\u003c/p\u003e \u003cp\u003eQuadriceps muscle strength showed a significant positive effect on RSI (B\u0026thinsp;=\u0026thinsp;0.077, p\u0026thinsp;=\u0026thinsp;0.031). However, the main effect of age (p\u0026thinsp;=\u0026thinsp;0.144) and the quadriceps strength \u0026times; age interaction (p\u0026thinsp;=\u0026thinsp;0.063) were not statistically significant. The overall model was moderate and significant (R\u0026sup2; = 0.207; F\u0026thinsp;=\u0026thinsp;6.537; p\u0026thinsp;=\u0026thinsp;0.001). Although the interaction term increased the explained variance by 3.8%, this increase was not statistically significant (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.038; p\u0026thinsp;=\u0026thinsp;0.063). The Johnson\u0026ndash;Neyman test indicated that the relationship was significant only in players under 17.62 years of age.\u003c/p\u003e \u003cp\u003eHamstring muscle strength, age, and their interaction were not statistically significant predictors (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Nevertheless, the overall model was moderate and significant (R\u0026sup2; = 0.201; F\u0026thinsp;=\u0026thinsp;6.277; p\u0026thinsp;=\u0026thinsp;0.001). The inclusion of the interaction term led to a 2.7% increase in explained variance, which was not statistically significant (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.027; p\u0026thinsp;=\u0026thinsp;0.115). The Johnson\u0026ndash;Neyman analysis showed that the relationship was significant only in players under 18.23 years of age.\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\u003eThe role of age in the effect of ROM and muscle strength parameters on vertical jump performance\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePredictor (Predicted=Vertical Jump)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLLCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eULCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e/\u003c/p\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e Change\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003eROM*Age*Vertical Jump\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Flexion ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.581\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.713\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.161\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.340\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e12.872\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20.533\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.802\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.975\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e32.091\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Flexion ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.139\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.042\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.222\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.096\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e10.907\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Extension ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.223\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.961\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.309\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.136\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.327\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e12.155\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.549\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.519\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.532\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e13.566\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Extension ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.170\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.056\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.003**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.281\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.059\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.083\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e9.279\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.003**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKnee Flexion ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.513\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.143\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.235\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.790\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e24.963\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e49.259\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e31.090\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e67.427\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKnee Flexion ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.349\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.066\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.481\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.217\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.185\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e27.729\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eStrength*Age*Vertical Jump\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuadriceps Strength (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.291\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.766\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.764\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.817\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.488\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e23.786\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.845\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e10.626\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuadriceps Strength \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.173\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.264\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.082\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.098\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e14.279\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHamstring Strength (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.792\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.328\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.146\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.437\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.366\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e14.434\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.517\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.517\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.495\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.539\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHamstring Strength \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.078\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.002**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-0.405\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.096\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.088\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e10.388\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.002**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eSignificance level (bold)\u003c/em\u003e **p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, \u003cem\u003eCM\u003c/em\u003e Centimeter, \u003cem\u003eKG\u003c/em\u003e Kilogram, \u003cem\u003eROM\u003c/em\u003e Range of motion, \u003cem\u003eSE\u003c/em\u003e Standard error, \u003cem\u003eLLCI\u003c/em\u003e Lower limit of the confidence interval, \u003cem\u003eULCI\u003c/em\u003e Upper limit of the confidence interval\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows that all models were found to be statistically significant as a result of multiple regression analyses regarding the effects of age-related interactions of lower extremity ROM and muscle strength variables on vertical jump performance.\u003c/p\u003e \u003cp\u003eFor hip flexion ROM, age, and the interaction term were all significant (B\u0026thinsp;=\u0026thinsp;2.581, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;20.533, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.139, p\u0026thinsp;=\u0026thinsp;0.001). The model demonstrated high and significant explanatory power (R\u0026sup2; = 0.340; F\u0026thinsp;=\u0026thinsp;12.872; p\u0026thinsp;=\u0026thinsp;0.000). The inclusion of the interaction term resulted in a significant 9.6% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.096; p\u0026thinsp;=\u0026thinsp;0.001). The Johnson\u0026ndash;Neyman test indicated significance only in players under 17.60 years of age.\u003c/p\u003e \u003cp\u003eFor hip extension ROM, age, and the interaction term were again significant (B\u0026thinsp;=\u0026thinsp;3.223, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;8.549, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.170, p\u0026thinsp;=\u0026thinsp;0.003). The model exhibited high explanatory power (R\u0026sup2; = 0.327; F\u0026thinsp;=\u0026thinsp;12.155; p\u0026thinsp;=\u0026thinsp;0.000), with an 8.3% significant increase in explained variance after adding the interaction term (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.083; p\u0026thinsp;=\u0026thinsp;0.003). Significance was observed only below 17.85 years of age.\u003c/p\u003e \u003cp\u003eFor knee flexion ROM, both main effects and the interaction term were significant (B\u0026thinsp;=\u0026thinsp;6.513, p\u0026thinsp;=\u0026thinsp;0.000; B\u0026thinsp;=\u0026thinsp;49.259, p\u0026thinsp;=\u0026thinsp;0.000; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.349, p\u0026thinsp;=\u0026thinsp;0.000). The model demonstrated high explanatory power (R\u0026sup2; = 0.500; F\u0026thinsp;=\u0026thinsp;24.963; p\u0026thinsp;=\u0026thinsp;0.000), and the interaction term contributed a significant 18.5% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.185; p\u0026thinsp;=\u0026thinsp;0.000). The Johnson\u0026ndash;Neyman analysis indicated significance below 18.02 years of age.\u003c/p\u003e \u003cp\u003eSimilarly, in the quadriceps strength model, both main effects and the interaction term were significant (B\u0026thinsp;=\u0026thinsp;3.291, p\u0026thinsp;=\u0026thinsp;0.000; B\u0026thinsp;=\u0026thinsp;7.236, p\u0026thinsp;=\u0026thinsp;0.000; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.173, p\u0026thinsp;=\u0026thinsp;0.000). The model showed high explanatory power (R\u0026sup2; = 0.488; F\u0026thinsp;=\u0026thinsp;23.786; p\u0026thinsp;=\u0026thinsp;0.000), with a significant 9.8% increase in explained variance due to the interaction term (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.098; p\u0026thinsp;=\u0026thinsp;0.000). Significance was limited to players under 17.98 years of age.\u003c/p\u003e \u003cp\u003eFor hamstring strength, both main effects and the interaction term were also significant (B\u0026thinsp;=\u0026thinsp;4.792, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;5.517, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.250, p\u0026thinsp;=\u0026thinsp;0.002). The model demonstrated high explanatory power (R\u0026sup2; = 0.366; F\u0026thinsp;=\u0026thinsp;14.434; p\u0026thinsp;=\u0026thinsp;0.000), with an 8.8% significant increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.088; p\u0026thinsp;=\u0026thinsp;0.002). The Johnson\u0026ndash;Neyman test indicated significance only in players under 17.99 years of age.\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\u003eThe role of age in the effect of ROM and muscle strength parameters on horizontal jump performance\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePredictor (Predicted=Horizontal Jump)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLLCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eULCI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e/\u003c/p\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e Change\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003eROM*Age*Horizontal Jump Distance\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Flexion ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.558\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.103\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.043*\u003c/b\u003e\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\u003e24.716\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.445\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e20.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66.222\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e49.658\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.186\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-32.701\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e165.146\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Flexion ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.591\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.360\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.104\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-1.308\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.125\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.104\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Extension ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.054\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14.947\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e47.035\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.457\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e21.019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54.108\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21.115\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.012*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.045\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e96.171\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHip Extension ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-1.651\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.468\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-2.584\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.718\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.090\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e12.427\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKnee Flexion ROM (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.761\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.892\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e16.064\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e59.458\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.478\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e22.918\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e250.909\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e86.893\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.005**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e77.809\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e424.010\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKnee Flexion ROM \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-1.948\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.632\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.003**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-3.206\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.689\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.066\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e9.509\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.003**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eStrength*Age*Horizontal Jump Distance\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuadriceps Strength (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.852\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.678\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11.548\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e38.155\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.553\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e30.918\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26.809\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.833\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-2.741\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e56.358\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuadriceps Strength \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-1.280\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.399\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.002**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-2.075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.484\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.061\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e10.264\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.002**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHamstring Strength (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42.144\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.365\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e19.503\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e64.785\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.466\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e21.860\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003e0.000**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20.874\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.986\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.112\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-4.996\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e46.743\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHamstring Strength \u0026times; Age Interaction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-2.211\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.665\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-3.535\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-0.886\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.079\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e11.057\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003e0.001**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eSignificance level (bold)\u003c/em\u003e *p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **p\u0026thinsp;\u0026lt;\u0026thinsp;0.01, \u003cem\u003eCM\u003c/em\u003e Centimeter, \u003cem\u003eKG\u003c/em\u003e Kilogram, \u003cem\u003eROM\u003c/em\u003e Range of motion, \u003cem\u003eSE\u003c/em\u003e Standard error, \u003cem\u003eLLCI\u003c/em\u003e Lower limit of the confidence interval, \u003cem\u003eULCI\u003c/em\u003e Upper limit of the confidence interval\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the results of multiple regression analyses examining the effects of age-related interactions between lower extremity ROM and muscle strength variables on horizontal jump performance, revealing statistically significant differences in some variables.\u003c/p\u003e \u003cp\u003eHip flexion ROM showed a significant and positive effect on horizontal jump performance (B\u0026thinsp;=\u0026thinsp;12.558, p\u0026thinsp;=\u0026thinsp;0.043). However, the main effect of age (p\u0026thinsp;=\u0026thinsp;0.186) and the hip flexion ROM \u0026times; age interaction (p\u0026thinsp;=\u0026thinsp;0.104) were not significant. The model demonstrated high and significant explanatory power (R\u0026sup2; = 0.445; F\u0026thinsp;=\u0026thinsp;20.005; p\u0026thinsp;=\u0026thinsp;0.000). Although the interaction term led to a 2% increase in explained variance, this contribution was not statistically significant (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.020; p\u0026thinsp;=\u0026thinsp;0.104). The Johnson\u0026ndash;Neyman test indicated significance only below 18.54 years of age.\u003c/p\u003e \u003cp\u003eFor hip extension ROM, age and the interaction term were significant (B\u0026thinsp;=\u0026thinsp;30.991, p\u0026thinsp;=\u0026thinsp;0.000; B\u0026thinsp;=\u0026thinsp;54.108, p\u0026thinsp;=\u0026thinsp;0.012; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.651, p\u0026thinsp;=\u0026thinsp;0.001). The model exhibited high explanatory power (R\u0026sup2; = 0.457; F\u0026thinsp;=\u0026thinsp;21.019; p\u0026thinsp;=\u0026thinsp;0.000), with a significant 9% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.090; p\u0026thinsp;=\u0026thinsp;0.001). Significance was limited to players under 17.84 years of age.\u003c/p\u003e \u003cp\u003eFor knee flexion ROM, all main effects and the interaction term were significant (B\u0026thinsp;=\u0026thinsp;37.761, p\u0026thinsp;=\u0026thinsp;0.001; B\u0026thinsp;=\u0026thinsp;250.909, p\u0026thinsp;=\u0026thinsp;0.005; B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.948, p\u0026thinsp;=\u0026thinsp;0.003). The model demonstrated high explanatory power (R\u0026sup2; = 0.478; F\u0026thinsp;=\u0026thinsp;22.918; p\u0026thinsp;=\u0026thinsp;0.000), with a significant 6.6% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.066; p\u0026thinsp;=\u0026thinsp;0.003). The Johnson\u0026ndash;Neyman analysis indicated significance below 18.23 years of age.\u003c/p\u003e \u003cp\u003eQuadriceps strength significantly and positively affected horizontal jump performance (B\u0026thinsp;=\u0026thinsp;24.852, p\u0026thinsp;=\u0026thinsp;0.000). The interaction term was also significant (B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;1.280, p\u0026thinsp;=\u0026thinsp;0.002), whereas the individual effect of age was not (p\u0026thinsp;=\u0026thinsp;0.075). The model showed high explanatory power (R\u0026sup2; = 0.553; F\u0026thinsp;=\u0026thinsp;30.918; p\u0026thinsp;=\u0026thinsp;0.000), with a significant 6.1% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.061; p\u0026thinsp;=\u0026thinsp;0.002). The Johnson\u0026ndash;Neyman test indicated significance only in players under 18.14 years of age.\u003c/p\u003e \u003cp\u003eSimilarly, hamstring strength was a significant predictor (B\u0026thinsp;=\u0026thinsp;42.144, p\u0026thinsp;=\u0026thinsp;0.000). Although the interaction term was significant (B\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;2.211, p\u0026thinsp;=\u0026thinsp;0.001), the individual effect of age was not statistically significant (p\u0026thinsp;=\u0026thinsp;0.112). The model demonstrated high explanatory power (R\u0026sup2; = 0.466; F\u0026thinsp;=\u0026thinsp;21.860; p\u0026thinsp;=\u0026thinsp;0.000), with a significant 7.9% increase in explained variance (R\u0026sup2; change\u0026thinsp;=\u0026thinsp;0.079; p\u0026thinsp;=\u0026thinsp;0.001). The Johnson\u0026ndash;Neyman analysis revealed that the relationship was significant only in players under 17.96 years of age.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study examined the effects of lower extremity ROM and muscle strength on motor performance, with a particular focus on the moderating role of age. Overall, the results indicate that these relationships are age-dependent, with stronger effects observed in younger athletes.\u003c/p\u003e \u003cp\u003eIn the first result of our study, the effects of ROM and muscle strength variables on RSI were evaluated in interaction with the age factor. In terms of ROM parameters, hip flexion, hip extension, and knee flexion ranges of motion demonstrated significant predictive effects on RSI in interaction with age. The significance of the interaction terms across all three variables indicates that the influence of these ranges of motion on RSI varies depending on age. These results suggest that hip joint mobility, in particular, is more effective during the transition from the amortization phase to the take-off phase, enhancing the efficiency of the stretch\u0026ndash;shortening cycle and thereby supporting RSI performance. According to the Johnson\u0026ndash;Neyman analyses, the fact that these effects were significant particularly in athletes under 17\u0026ndash;18 years of age suggests that, developmentally, joint mobility is more determinant for reactive performance at younger ages. The incomplete maturation of neuromuscular coordination during these years may increase the contribution of range of motion to performance [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, with increasing age, the influence of mobility on agility-based outcomes such as RSI appears to diminish, being replaced by strength, speed, and synchronized muscle activation [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWith regard to strength variables, quadriceps muscle strength significantly and positively predicted RSI, whereas hamstring muscle strength did not demonstrate a significant effect. Although the interaction with age was not significant for quadriceps strength, the relationship appeared more pronounced in the younger age groups. This result may be attributed to the quadriceps muscles serving as the primary propulsive power during RSI tasks [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In contrast, the supportive role of the hamstring muscles may not be sufficient to independently explain RSI performance [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Furthermore, age-related improvements in the direction, timing, and coordination of strength production appear to enhance the contribution of the quadriceps muscles to performance, whereas this effect seems more limited at younger ages [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the second result of our study, the effects of ROM and muscle strength variables on vertical jump performance were evaluated in interaction with age. In terms of ROM parameters, the significance of both the main effects and the age interactions for hip flexion, hip extension, and knee flexion ROM indicates that the contribution of these parameters to vertical jump performance varies according to age. The fact that these effects were significant particularly in individuals under 17\u0026ndash;18 years of age suggests that joint range of motion is more determinant for jump performance during developmental stages. In this age group, as synchronized motor unit recruitment, explosive power production, and coordination are not yet fully developed, joint mobility may provide a compensatory advantage [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. However, the disappearance of these effects with increasing age suggests that, in complex motor outputs such as jumping, ROM is progressively replaced by greater contributions from strength, speed, and neuromuscular control [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRegarding strength parameters, the significant interactions of both quadriceps and hamstring muscle strength with age indicate that the influence of muscle strength on vertical jump performance also differs according to age. Since the quadriceps muscle acts as the primary extensor during jumping, increases in strength at younger ages may significantly enhance jump height. However, with advancing age and the development of technical proficiency as well as intra- and inter-muscular coordination, the direct impact of strength on performance appears to weaken [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Similarly, the relationship that was significant for hamstring strength at younger ages lost its significance with increasing age. This may be explained by the supportive role of the hamstring muscles during jumping, as their contribution is more related to control, stabilization, and the landing phase [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Overall, both ROM and muscle strength variables appear to exert age-sensitive effects on jump performance, with their influence diminishing or being replaced by other motor factors as part of the developmental process.\u003c/p\u003e \u003cp\u003eIn the third result of our study, the effects of ROM and muscle strength variables on horizontal jump performance were evaluated in interaction with the age factor. In terms of ROM parameters, hip extension and knee flexion ROM were found to influence horizontal jump performance at different levels depending on age. The fact that these ranges of motion were significant predictors particularly in individuals under 17\u0026ndash;18 years of age suggests that joint mobility plays a greater role during the wide propulsion angle and prolonged acceleration phase required in horizontal jumping. Since strength production time is longer in younger age groups, a greater range of motion may support this process and increase jump distance [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. However, with increasing age, propulsion time shortens and movement efficiency improves, relatively reducing the effect of ROM. Although hip flexion ROM did not demonstrate a significant interaction with age, it was found to be significant in individuals under 18 years of age. This result suggests that hip flexion may provide an advantage for younger athletes during the forward trunk flexion and loading phase required for horizontal jumping [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRegarding muscle strength variables, the age-dependent effects observed for both quadriceps and hamstring strength indicate that the role of strength in horizontal jump performance changes throughout the developmental process. Particularly at younger ages, insufficient integration of muscle strength with technical control may cause strength to be reflected more directly in performance [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. This may explain why quadriceps strength emerged as a significant determinant in athletes under 18 years of age. Similarly, the fact that hamstring strength was significant only in the younger age group may be attributed to the role of these muscles in maintaining the balance between hip extension and knee flexion during jumping, thereby contributing to propulsion efficiency. However, with increasing age and improved movement economy, this contribution becomes less critical [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Overall, the effects of ROM and muscle strength variables on horizontal jump performance appear to vary according to age; these physical characteristics exert a more direct influence at younger ages, whereas technical proficiency and movement strategies become more prominent with advancing age.\u003c/p\u003e \u003cp\u003eThese results are consistent with the literature reporting age-related effects of lower extremity mobility and muscle strength on motor performance. For example, it has been reported that during adolescence, the stretch\u0026ndash;shortening cycle improves significantly with the development of the neuromuscular system, with quadriceps muscle strength and lower extremity flexibility playing a determinant role in this improvement [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Although both quadriceps and hamstring strength increase with age, muscle imbalances between these groups are frequently observed in younger age groups (particularly 12\u0026ndash;16 years), which may contribute to performance limitations and inefficient functioning of the stretch\u0026ndash;shortening cycle [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Furthermore, the contribution of hip and knee ROM to reactive jump performance provides a more pronounced advantage in age groups where neuromuscular coordination has not yet fully matured [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Similarly, vertical jump performance has been shown to be age-sensitive; during the prepubertal period, insufficient elastic energy reutilization limits performance, whereas in adolescence, improvements in muscle\u0026ndash;tendon structure and neuromuscular coordination result in marked performance enhancements [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In young adulthood, maximal strength production and explosive power capacity further elevate this development to its highest level [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOn the other hand, it has been reported that during adolescence, hip and knee joint range of motion may exert a more pronounced influence on explosive jump outcomes than strength or neuromuscular proficiency [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. In particular, in the 12\u0026ndash;16 age group, the contribution of such mobility to performance becomes more evident [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Additionally, in motor skills such as horizontal jumping, which require a wide propulsion angle and prolonged acceleration, the importance of specific ROM values such as hip extension and knee flexion has been emphasized. It has also been reported that age-related increases in joint mobility positively affect horizontal jump performance in young female athletes [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Moreover, it has been suggested that evaluating muscle strength balance and mobility together enables more accurate prediction of jump performance in young athletes [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. In this context, the age-dependent interaction effects identified in our study are grounded in a biomechanically and developmentally meaningful framework in light of the existing literature.\u003c/p\u003e"},{"header":"Limitations","content":"\u003cp\u003eThis study has several limitations. The inclusion of only elite male soccer players limits the generalizability of the results to different sexes and sports disciplines. Due to its cross-sectional design, the study does not allow for causal inferences. Age groups were classified according to chronological age rather than biological maturation, which may have overlooked individual developmental differences. Additionally, psychological and environmental factors such as sleep, fatigue, and motivation were not controlled. These limitations should be taken into consideration when interpreting the results.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis research revealed that the effects of lower extremity range of motion and muscle strength variables on motor performance differ significantly according to age. In particular, the more pronounced effects of physical parameters on both RSI and jump performance in individuals under 17\u0026ndash;18 years of age indicate that range of motion and muscle strength are more directly reflected in motor outputs within this age group. However, with increasing age, the influence of these variables decreases, and motor performance becomes more dependent on complex processes such as the direction and timing of strength production and neuromuscular control. The result that broader age-range groups served as significant predictors particularly in horizontal jump performance suggests that this motor skill more clearly reflects age-related development. In contrast, the absence of age as an independent determinant in tasks such as RSI and vertical jump indicates that age assumes an indirect role, operating only in interaction with physical characteristics. Accordingly, the development of motor performance appears to be associated not merely with advancing age, but with the extent to which age-specific physical capacities are functionally optimized. Therefore, training programs should consider developmental characteristics specific to each age group. In particular, in U15\u0026ndash;U17 groups, maintaining ROM capacity and emphasizing multidirectional strength development (such as eccentric strength training, isokinetic exercises, and plyometric preparation) should be prioritized, while technical skill acquisition should be progressively integrated in parallel with the development of neuromuscular control.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCM\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Centimeter\u003c/p\u003e\n\u003cp\u003eDL\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Dominant leg\u003c/p\u003e\n\u003cp\u003eICC\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Intraclass correlation coefficients\u003c/p\u003e\n\u003cp\u003eKG\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Kilograms\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLLCI\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Lower limit of the confidence interval\u003c/p\u003e\n\u003cp\u003eROM\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Range of motion\u003c/p\u003e\n\u003cp\u003eRSI\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Reactive strength index\u003c/p\u003e\n\u003cp\u003eSE\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Standard error\u003c/p\u003e\n\u003cp\u003eULCI\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Upper limit of the confidence interval\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to express their sincere gratitude to the Recep Tayyip Erdoğan University Development Foundation for their financial support. The authors also thank all participants for their valuable contribution to the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the design and planning of the study. Data collection, analysis, and interpretation were performed by H.İ.\u0026Ccedil;., R.F.K., E.T. and H.K. The first draft of the manuscript was written by E.T. and previous versions were reviewed by all authors. All authors read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study has been supported by the Recep Tayyip Erdoğan University Development Foundation (Grant number: 02026004007238).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis cross-sectional study was approved by the Ethics Committee of the Faculty of Social and Human Sciences at Recep Tayyip Erdogan University (Date: 18/02/2026; Approval No: 2026/75). All procedures were conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants and their legal guardians, and permission was secured from the affiliated sports club prior to data collection. All relevant documents were submitted for ethical review in advance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\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"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eTurner AN, Stewart PF. Strength and conditioning for soccer players. 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Sports. 2019;7(7):158. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/sports7070158\u003c/span\u003e\u003cspan address=\"10.3390/sports7070158\" 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-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Age differences, Explosive power, Neuromuscular performance, Soccer players, Youth athletes","lastPublishedDoi":"10.21203/rs.3.rs-9372764/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9372764/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eExplosive power is a key determinant of soccer performance and is closely associated with lower extremity joint function, particularly hip and knee range of motion (ROM) and muscle strength. These factors contribute to essential actions such as jumping, sprinting, and rapid changes of direction; however, their influence may vary across developmental stages due to age-related neuromuscular and physical differences. Despite existing evidence linking strength and flexibility to motor performance, the moderating role of age in these relationships remains unclear in youth soccer players. Therefore, this study aimed to investigate the effects of hip and knee joint ROM and muscle strength on motor performance and to evaluate the moderating role of age in these associations.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA total of 59 male football players from the youth academies of professional teams participated in the study. ROM values of the hip/knee joints, as well as quadriceps/hamstring muscle strength, were measured; subsequently, motor performance assessments were conducted. The data were analyzed using multiple regression models including interaction terms with age, and regions of significance were determined using the Johnson\u0026ndash;Neyman technique.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eFor the reactive strength index, hip and knee ROM and quadriceps strength were identified as significant predictors; however, these effects were particularly pronounced in soccer players under the age of 17\u0026ndash;18 (r\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.076\u0026ndash;0.239; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Similarly, for vertical and horizontal jump performance, hip and knee ROM, as well as quadriceps and hamstring muscle strength, were significant predictors, with these effects again being more evident in players under the age of 17\u0026ndash;18 (r\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.061\u0026ndash;0.553; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eLower extremity physical characteristics influence motor performance in an age-dependent manner, with stronger effects observed in players under 17\u0026ndash;18 years and reduced effects at older ages. Therefore, structuring training programs in these age groups to prioritize the development of range of motion and strength, integrated with exercises that support neuromuscular control, is of great importance for enhancing performance and reducing the risk of injury.\u003c/p\u003e","manuscriptTitle":"The moderating role of age in the effect of hip and knee joint functions on explosive power performance in soccer players","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-22 13:15:51","doi":"10.21203/rs.3.rs-9372764/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"304184554886665659574781538690148129692","date":"2026-05-10T20:06:27+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"202936085022261889490950251046895777356","date":"2026-05-09T03:35:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-06T18:40:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"217370206924472187327582219973964919538","date":"2026-04-30T10:52:32+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-15T06:47:03+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-14T06:27:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-11T01:17:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-11T01:16:53+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Sports Science, Medicine and Rehabilitation","date":"2026-04-09T22:41:48+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-sports-science-medicine-and-rehabilitation","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ssmr","sideBox":"Learn more about [BMC Sports Science, Medicine and Rehabilitation](http://bmcsportsscimedrehabil.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ssmr/default.aspx","title":"BMC Sports Science, Medicine and Rehabilitation","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"fbffa77d-f2b4-4b0c-bba6-7412963e2c10","owner":[],"postedDate":"April 22nd, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"304184554886665659574781538690148129692","date":"2026-05-10T20:06:27+00:00","index":37,"fulltext":""},{"type":"reviewerAgreed","content":"202936085022261889490950251046895777356","date":"2026-05-09T03:35:04+00:00","index":36,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-06T18:40:59+00:00","index":29,"fulltext":""},{"type":"reviewerAgreed","content":"217370206924472187327582219973964919538","date":"2026-04-30T10:52:32+00:00","index":26,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-22T13:15:51+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-22 13:15:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9372764","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9372764","identity":"rs-9372764","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}