Association of Knee Extension Torque, Velocity and Power with Chronological Age, Maturity Status and Physical...

Background: This study aimed to assess the effects of age and maturity status on the knee extension torque-velocity (T-V) relationship, muscle power, and physical performance in prepubertal boys. Methods: This cross-sectional study included 53 prepubertal boys (9-13 years old) who underwent a physical and maturity status examination. Knee extension T-V relationship was assessed using an isokinetic device, and maximal isometric torque (T₀), maximal unloaded velocity, maximum muscle power, and T-V slope (T-V_slope) were derived. Physical performance was assessed using the countermovement jump (CMJ) height. Linear regression models were used, and the level of significance was set at p ≤ 0.05. Results: All torque and power parameters were significantly correlated with age (r = 0.49-0.58) and maturity status (r = 0.74-0.78) (all p < 0.05). No associations were found for velocity-related parameters (r = 0.20) or T-V_slope relative to T₀ (r = 0.18) (both p > 0.05). Interestingly, the associations disappeared when muscle function parameters were normalized to body mass (all p > 0.05), whereas normalization to height squared only weakened the associations, which remained statistically significant (p < 0.05). Finally, CMJ height was most strongly associated with T-V and power parameters normalized to body mass, especially at higher contraction velocities. Conclusions: Torque and muscle power derived from the knee extension T-V relationship increased as a function of age and maturity status in prepubertal boys. These associations vanished upon adjustment for body mass, while normalization to height squared only weakened the correlations. Muscle function produced at faster contraction velocities and normalized to body mass emerged as the best indicator of functional muscle performance in prepubertal children among the studied neuromuscular parameters.