Xu Yongxin, Yang Yang, He Siyuan, Yang Chenhao, Zhang Shen, Fu Weijie, Li Lu
Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai 200438, China.
Shanghai Ulink Bilingual School, Shanghai 201615, China.
Gait Posture. 2025 Jun;119:163-170. doi: 10.1016/j.gaitpost.2025.03.008. Epub 2025 Mar 18.
Fatigue changes muscle activation patterns as an adaptation strategy in multi-joint movements. However, due to groups of muscles involved in running, the across-muscle neurological regulation before and after fatigue is unclear. The central nervous system may employ low-dimensional modular structures, known as muscle synergies, to describe the muscle coordination in a multi-joint movement such as running.
This study aimed to explore the effect of fatigue on lower extremity muscle synergy and biomechanical characteristics in running.
Twelve healthy male participants were recruited. The kinematic, kinetic, and surface electromyography data of nine muscles (i.e., gluteus maximus, biceps femoris, rectus femoris, vastus medialis, vastus lateralis, tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and soleus) were synchronously recorded on a treadmill at 12 km/h before and after a load-increasing fatigue intervention. Muscle synergy was calculated by the non-negative matrix factorization algorithm. Muscle weight and activation curves were used to identify the co-activation before and after fatigue.
Maximum ankle plantarflexion velocity, maximum knee flexion angle, and hip range of motion significantly increased after fatigue. Vertical stiffness and work in the lower extremity significantly decreased after fatigue. Six muscle synergies (SYN1-6) were clustered before and after fatigue, corresponding to four major functions in the running gait cycle. The number of muscle synergy did not change significantly after fatigue, while the muscle weights and activation curve changed.
Muscle synergies were stabilized and were less affected by fatigue, corresponding to specific biomechanical functions within the running gait cycle. Meanwhile, changes in muscle weights and activation curves reflected neuromuscular adaptations to fatigue and may be associated with alterations in lower extremity kinematics during continuous movement after fatigue.
疲劳会改变肌肉激活模式，作为多关节运动中的一种适应策略。然而，由于跑步涉及多组肌肉，疲劳前后跨肌肉的神经调节尚不清楚。中枢神经系统可能采用低维模块化结构，即肌肉协同作用，来描述跑步等多关节运动中的肌肉协调。
本研究旨在探讨疲劳对跑步时下肢肌肉协同作用和生物力学特征的影响。
招募了12名健康男性参与者。在递增负荷疲劳干预前后，于跑步机上以12公里/小时的速度同步记录九块肌肉（即臀大肌、股二头肌、股直肌、股内侧肌、股外侧肌、胫骨前肌、腓肠肌内侧头、腓肠肌外侧头和比目鱼肌）的运动学、动力学和表面肌电图数据。通过非负矩阵分解算法计算肌肉协同作用。利用肌肉权重和激活曲线来识别疲劳前后的共同激活。
疲劳后最大踝关节跖屈速度、最大膝关节屈曲角度和髋关节活动范围显著增加。疲劳后下肢垂直刚度和功显著降低。疲劳前后聚类出六种肌肉协同作用（SYN1 - 6），对应跑步步态周期中的四种主要功能。疲劳后肌肉协同作用的数量没有显著变化，而肌肉权重和激活曲线发生了变化。
肌肉协同作用稳定，受疲劳影响较小，对应跑步步态周期内特定的生物力学功能。同时，肌肉权重和激活曲线的变化反映了神经肌肉对疲劳的适应，可能与疲劳后持续运动过程中下肢运动学的改变有关。
