Seasonal Variation in Isokinetic Peak Torque in Youth Soccer Players

The aim of the study was to investigate the seasonal variation in the strength of the knee flexors and extensors in highly trained youth soccer players. The players (n=16; age 16.7±0.7) were measured at the end of the competitive season, at the beginning of the off-season and during the sixth week of a new competitive season. Isokinetic concentric peak torque was measured at 60°·s-1, 180°·s-1, 360°·s-1 in a sitting position. The testing range of motion was set from 10–90° of knee flexion. Players performed a set of six maximal repetitions for both the dominant and non-dominant limb. Average values of peak torque significantly changed during the observed periods. Significant differences (p<.05) between the three measurement sessions were noted with respect to the knee flexors at all angular velocities. A post-hoc test confirmed a significant increase between the first and the second measurement for flexion in both the dominant (180°·s-1; p=.033) and nondominant legs (360°·s-1; p=.004). A significant increase was also found between the first and the third session for both limbs during the knee flexion at all angular velocities. The results indicate that peak torque values of knee flexors and extensors varied differently in trained youth soccer players depending on muscle group and movement velocity with statistically significant changes in knee flexors only.