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动作的团队球类项目青年运动员与非跳跃类团队球类项目青年运动员的膝关节屈肌与伸肌运动表现。本研究纳入两组青年男性运动员：跳跃组（n=46，涵盖排球、篮球及手球运动员）与非跳跃专项组（n=44，涵盖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表现，本研究采用等速测力仪（isokinetic dynamometer）以60°/s的速度进行向心模式测试。本研究分析的变量包括：体质量标准化峰值扭矩（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）。为判定单侧肌肉功能缺陷，本研究以I:Q比值低于50%作为判定标准；为判定双侧肌肉功能不对称，则以双侧肢体间峰值扭矩差值超过10%作为判定标准。研究结果显示，两组运动员、不同测试肢体以及二者交互作用下的膝关节屈肌与伸肌运动表现均无显著差异。对比峰值扭矩与I:Q比值的显著异常情况时，跳跃组优势侧肢体的I:Q比值失衡运动员占比更高（58.6% vs 25%，p=0.001）。组内对比结果显示，非跳跃专项组运动员在伸肌与屈肌的峰值扭矩、屈肌的功率以及I:Q比值上存在肢体间差异。综上，无论所属组别，从事团队球类项目的青年运动员均存在肌肉不对称情况，本研究建议引入肌肉失衡预防方案以降低此类不对称带来的负面影响。