Understanding the neuromechanical responses to perturbations in humans may help to explain the reported improvements in stability performance and muscle strength after perturbation-based training. In this study, we investigated the effects of perturbations, induced by unstable surfaces, on the mechanical loading and the modular organization of motor control in the lower limb muscles during lunging forward and backward. Fifteen healthy adults performed 50 forward and 50 backward lunges on stable and unstable ground. Ground reaction forces, joint kinematics, and the electromyogram (EMG) of 13 lower limb muscles were recorded. We calculated the resultant joint moments and extracted muscle synergies from the stepping limb. We found sparse alterations in the resultant joint moments and EMG activity, indicating a little if any effect of perturbations on muscle mechanical loading. The time-dependent structure of the muscle synergy responsible for the stabilization of the body was modified in the perturbed lunges by a shift in the center of activity (later in the forward and earlier in the backward lunge) and a widening (in the backward lunge). Moreover, in the perturbed backward lunge, the synergy related to the body weight acceptance was not present. The found modulation of the modular organization of motor control in the unstable condition and related minor alteration in joint kinetics indicates increased control robustness that allowed the participants to maintain functionality in postural challenging settings. Triggering specific modulations in motor control to regulate robustness in the presence of perturbations may be associated with the reported benefits of perturbation-based training.

中文翻译：

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存在扰动时动态平衡任务的神经力学

了解人类对扰动的神经力学反应可能有助于解释所报告的基于扰动的训练后稳定性表现和肌肉力量的改善。在这项研究中，我们研究了由不稳定表面引起的扰动对向前和向后冲刺过程中下肢肌肉的机械载荷和运动控制的模块化组织的影响。15 名健康成年人在稳定和不稳定的地面上进行了 50 次向前和 50 次向后弓步。记录了 13 条下肢肌肉的地面反作用力、关节运动学和肌电图 (EMG)。我们计算了合成的关节力矩并从踏步肢体中提取了肌肉协同作用。我们发现所产生的关节力矩和 EMG 活动发生了稀疏变化，表明微扰对肌肉机械负荷的影响（如果有的话）。负责稳定身体的肌肉协同作用的时间依赖性结构在受扰的弓步中通过活动中心的转移（在向前弓步中较早，在向后弓步中较早）和加宽（在向后弓步中）进行了修改）。此外，在扰动的向后弓步中，不存在与体重接受相关的协同作用。在不稳定条件下发现的运动控制模块化组织的调制和关节动力学的相关微小改变表明控制鲁棒性增加，使参与者能够在姿势挑战设置中保持功能。