Changes In Isokinetic Muscle Strength Of The Knee In Elite Female Adolescent Volleyball Players

Abstract

There are few reports regarding changes in joint muscle strength in elite-level adolescent athletes after systematic training. PURPOSE: This study followed elite-level adolescent female volleyball players for 4 years to analyze changes in knee joint muscle strength after systematic training. METHODS: We performed isokinetic muscle strength testing of the knee at angular velocities of 60°/s and 240°/s in 16 elite-level adolescent female volleyball players. RESULTS: Compared with baseline, in adulthood (4 years later), peak torque (240°/s) in the right flexor and extensor increased by 13.94% (78.38 ± 8.87 vs 89.31 ± 13.26 Nm, p = 0.029) and 16.02% (134.19 ± 20.38 vs 155.69 ± 24.80 Nm, p = 0.034), but the increase was not statistically significant for the left knee (p > 0.05). Left and right flexor endurance ratios increased by 17.00% (0.59 ± 0.13 vs 0.69 ± 0.12, p = 0.041) and 14.75%(0.61 ± 0.12 vs 0.70 ± 0.13 Nm, p = 0.037), respectively. The difference between bilateral homonymous muscles was more than 15%, in adolescence, at 60°/s, n = 1 for flexors, n = 5 for extensors; at 240°/s, n = 2 for flexors, n = 4 for extensors and in adulthood, at 60°/s, n = 1 for flexors, n = 2 for extensors; at 240°/s n = 1 case for flexors, n = 3 for extensors. CONCLUSION: After 4 years of systematic training, elite-level adolescent female volleyball players had significant increased (240°/s) peak torque for the dominant knee, and the endurance ratio of bilateral flexor muscles was improved. We recommend strengthening the knee flexor muscle group during training to increase hamstrings-to-quadriceps ratio values and reduce the risk of knee injury.