Mersmann Falk, Charcharis Georgios, Bohm Sebastian, Arampatzis Adamantios
Department of Training and Movement Sciences, Humboldt-Universität zu BerlinBerlin, Germany.
Berlin School of Movement ScienceBerlin, Germany.
Front Physiol. 2017 Jun 16;8:417. doi: 10.3389/fphys.2017.00417. eCollection 2017.
Though the plasticity of human tendons is well explored in adults, it is still unknown how superimposed mechanical loading by means of athletic training affects the properties of tendons during maturation. Due to the increased responsiveness of muscle to mechanical loading, adolescence is an important phase to investigate the effects of training on the mechanical properties of tendons. Hence, in the present study we compared vastus lateralis (VL) architecture, muscle strength of the knee extensor muscles and patellar tendon mechanical properties of male and female adolescent elite athletes to untrained boys and girls. Twenty-one adolescent volleyball athletes (A; 16.7 ± 1 years; 12 boys, 9 girls) and 24 similar-aged controls (C; 16.7 ± 1 years; 12 boys and girls, respectively) performed maximum isometric contractions on a dynamometer for the assessment of muscle strength and, by integrating ultrasound imaging, patellar tendon mechanical properties. Respective joint moments were calculated using an inverse dynamics approach and an electromyography-based estimation of antagonistic contribution. Additionally, the VL pennation angle, fascicle length and muscle-thickness were determined in the inactive state by means of ultrasound. Adolescent athletes produced significantly greater knee extension moments (normalized to body mass) compared to controls (A: 4.23 ± 0.80 Nm/kg, C: 3.57 ± 0.67 Nm/kg; = 0.004), and showed greater VL thickness and pennation angle (+38% and +27%; < 0.001). Tendon stiffness (normalized to rest length) was also significantly higher in athletes (A: 86.0 ± 27.1 kN/strain, C: 70.2 ± 18.8 kN/strain; = 0.04), yet less pronounced compared to tendon force (A: 5785 ± 1146 N, C: 4335 ± 1015 N; < 0.001), which resulted in higher levels of tendon strain during maximum contractions in athletes (A: 8.0 ± 1.9%, C: 6.4 ± 1.8%; = 0.008). We conclude that athletic volleyball training provides a more efficient stimulus for muscle compared to tendon adaptation, which results in an increased demand placed upon the tendon by the working muscle in adolescent volleyball athletes. Besides implications for sport performance, these findings might have important consequences for the risk of tendon overuse injury.
虽然在成年人中已经对人类肌腱的可塑性进行了充分研究，但通过体育训练施加的叠加机械负荷如何影响肌腱在成熟过程中的特性仍不清楚。由于肌肉对机械负荷的反应性增加，青春期是研究训练对肌腱机械性能影响的重要阶段。因此，在本研究中，我们比较了男女青少年精英运动员的股外侧肌（VL）结构、膝伸肌肌肉力量和髌腱机械性能与未受过训练的男孩和女孩。21名青少年排球运动员（A组；16.7±1岁；12名男孩，9名女孩）和24名年龄相仿的对照组（C组；16.7±1岁；分别为12名男孩和女孩）在测力计上进行最大等长收缩，以评估肌肉力量，并通过整合超声成像来评估髌腱机械性能。使用逆动力学方法和基于肌电图的拮抗肌贡献估计来计算各自的关节力矩。此外，通过超声在非活动状态下测定VL的羽状角、肌束长度和肌肉厚度。与对照组相比，青少年运动员产生的膝关节伸展力矩（按体重归一化）明显更大（A组：4.23±0.80 Nm/kg，C组：3.57±0.67 Nm/kg；P = 0.004），并且显示出更大的VL厚度和羽状角（分别增加38%和27%；P < 0.001）。运动员的肌腱刚度（按静息长度归一化）也明显更高（A组：86.0±27.1 kN/应变，C组：70.2±18.8 kN/应变；P = 0.04），但与肌腱力相比不太明显（A组：5785±1146 N，C组：4335±1015 N；P < 0.001），这导致运动员在最大收缩时肌腱应变水平更高（A组：8.0±1.9%，C组：6.4±1.8%；P = 0.008）。我们得出结论，与肌腱适应相比，排球运动训练对肌肉提供了更有效的刺激，这导致青少年排球运动员工作肌肉对肌腱的需求增加。除了对运动表现的影响外，这些发现可能对肌腱过度使用损伤的风险产生重要影响。
