Knee flexor and extensor muscles performance comparison in youth team sports with and without jumping

Abstract This study aims to compare the performance of knee flexor and extensor muscles in young athletes of team sports with and without jumping as specific movement. There were two groups with young male athletes: the jumping group (n 46, volleyball, basketball and handball athletes) and group without jumping characteristics (n=44, futsal and soccer athletes). To evaluate the muscle performance of the flexors and extensors of the knee, we used an isokinetic dynamometer at a speed of 60°/s in concentric mode. The variables analyzed were peak torque normalized by body mass (PT), total work (TW), power (POW) and agonist/antagonist ratio (I:Q). To estimate unilateral deficits, we considered the values of the I:Q ratio less than 50%, and for bilateral deficits, asymmetries between the limbs greater than 10% for PT. There were no significant differences in the performance of knee flexor and extensor muscles between the groups, limbs and their interaction. When comparing significant deficits in PT and in the I:Q Ratio, a greater number of athletes in the jumping group showed imbalances in the I:Q ratio in the dominant limb (58.6% versus 25%, p=0.001). In the intragroup comparison, the group of athletes without jumping characteristics showed a difference between the limbs in the variables PT of extensors and flexors, in the flexors POW and in the I:Q ratio. Young athletes practicing team sports, regardless of the group, showed muscle asymmetries, and we suggest the insertion prevention programs in order to minimize them.

摘要 本研究旨在对比以跳跃为专项运动动作的团队运动青年运动员与非跳跃类团队运动青年运动员的膝关节屈肌与伸肌性能差异。本研究招募两组青年男性运动员：跳跃组（n=46，包含排球、篮球及手球运动员）与非跳跃专项组（n=44，包含五人制足球及足球运动员）。为评估膝关节屈肌与伸肌的肌肉性能，本研究以60°/s的向心收缩模式使用等速测力仪（isokinetic dynamometer）进行检测。本次分析的指标包括：体质量标准化峰扭矩（peak torque normalized by body mass, PT）、总功（total work, TW）、功率（power, POW）以及主动肌/拮抗肌比值（agonist/antagonist ratio, I:Q）。针对单侧肌力缺陷，本研究以I:Q比值低于50%作为判定标准；针对双侧肌力缺陷，则以四肢间峰扭矩差值超过10%作为判定依据。研究结果显示，两组、双侧肢体及其交互作用下，膝关节屈肌与伸肌的性能均无显著差异。对比PT与I:Q比值的显著缺陷情况时，跳跃组优势侧肢体出现I:Q比值失衡的运动员占比更高（58.6% vs 25%，p=0.001）。组内比较结果显示，非跳跃专项组运动员在伸肌与屈肌的PT、屈肌的POW以及I:Q比值上存在肢体间差异。无论所属组别，参与团队运动的青年运动员均存在肌肉不对称性，因此建议引入肌肉失衡预防项目以降低此类不对称性的发生。