Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA.
Gait Posture. 2013 Sep;38(4):993-7. doi: 10.1016/j.gaitpost.2013.05.009. Epub 2013 Jun 17.
The gastrocnemius and soleus both contribute to the ankle plantarflexor moment during the mid- and terminal stance phases of gait. The gastrocnemius also generates a knee flexion moment that may lead to dynamic function that is unique from the soleus. This study used a muscle stimulation protocol to experimentally compare the contributions of individual plantarflexors to vertical support, forward propulsion and center of pressure (CoP) movement during normal gait. Twenty subjects walked on an instrumented treadmill at self-selected speeds with stimulating surface electrodes affixed over the medial gastrocnemius and soleus muscles. Short duration pulse trains (90 ms) were used to stimulate either the gastrocnemius or soleus at 20% or 30% of the gait cycle (GC) of random strides. Changes in ground reactions between stimulated and non-stimulated strides were evaluated to characterize the influence of each muscle on whole body movement during mid- (stimulation onset at 20% GC) and late (30% GC) stance. The gastrocnemius and soleus each induced an increase in vertical support and anterior progression of the CoP in mid-stance. However, late stance gastrocnemius activity induced forward acceleration, while both mid- and terminal stance soleus activity induced braking of forward velocity. The results suggested that the individual plantarflexors exhibit unique functions during normal gait, with the two muscles having opposite effects on forward propulsion. These empirical results are important both for enhancing the veracity of models used to predict muscle function in gait and also clinically as physicians seek to normalize gait in patients with plantarflexor dysfunction.
比目鱼肌和腓肠肌在步态的中间和末期都有助于踝关节跖屈肌力矩。腓肠肌还产生膝关节屈曲力矩，这可能导致与比目鱼肌不同的动态功能。本研究使用肌肉刺激方案，通过实验比较了个体跖屈肌在正常步态中对垂直支撑、向前推进和中心压力（CoP）运动的贡献。20 名受试者在装有刺激表面电极的仪器化跑步机上以自选择速度行走，电极贴在腓肠肌和比目鱼肌的内侧。使用持续时间为 90ms 的短脉冲序列，以 20%或 30%的步态周期（GC）随机步幅刺激腓肠肌或比目鱼肌。评估刺激和非刺激步之间的地面反作用力变化，以表征在中间（刺激开始于 20%GC）和后期（30%GC）站立期间，每个肌肉对全身运动的影响。腓肠肌和比目鱼肌在中间站立时都能增加垂直支撑和 CoP 的前向推进。然而，后期站立时的腓肠肌活动会引起向前加速，而中站和终站的比目鱼肌活动都会引起向前速度的制动。结果表明，个体跖屈肌在正常步态中表现出独特的功能，两个肌肉对向前推进有相反的影响。这些实验结果对于提高用于预测步态中肌肉功能的模型的准确性以及临床医生试图使跖屈肌功能障碍患者的步态正常化都非常重要。
