Movement-Interactions-Performance, MIP, Nantes Université, Nantes, France.
Laboratory of Functional Morphology, Department of Biology, University of Antwerp, Antwerp, Belgium.
J Appl Physiol (1985). 2023 Jan 1;134(1):105-115. doi: 10.1152/japplphysiol.00587.2022. Epub 2022 Dec 1.
The human soleus muscle is anatomically divided into four separate anatomical compartments. The functional role of this compartmentalization remains unclear. Here, we tested the hypothesis that the common synaptic input to motor units between the medial and lateral posterior compartments is less than within each compartment. Fourteen male participants performed three different heel-raise tasks that were considered to place a different mechanical demand on the medial and lateral soleus compartments. High-density electromyography (EMG) signals from the medial and lateral soleus compartments and the medial gastrocnemius of the right leg were decomposed into individual motor unit spike trains. The coherence between cumulative spike trains of the motor units was estimated. The coherence analysis was also repeated for motor units that were matched across all three tasks. Furthermore, we calculated the ratio of significant correlations between the spike trains of pairs of motor units. We observed that the coherence between motor units of the two soleus compartments was similar as the coherence between motor units within each compartment, regardless of the task. The correlation analysis performed on pairs of motor units confirmed these results. We conclude that the level of common synaptic input between the motor units innervating the medial and lateral posterior soleus compartment is not different than the common synaptic input between motor units innervating each of these compartments, which contrasts with findings from previous studies on finger muscles. This suggests that there is no independent neural control for the individual posterior soleus compartments. The human soleus muscle is anatomically subdivided into four compartments. The functional role for this compartmentalization remains unknown. Here, we showed that, contrary to previous findings in finger muscles, the common synaptic input between motor units innervating the medial and lateral posterior soleus compartment was similar as that between motor units within the individual compartments. We suggest that the contradictory findings with other compartmentalized muscles may be explained by differences in muscle-tendon anatomy and function.
人类比目鱼肌在解剖上可分为四个独立的解剖室。这种分区的功能作用尚不清楚。在这里，我们测试了这样一个假设，即内侧和外侧后室之间运动单位的共同突触传入小于每个室内部。14 名男性参与者进行了三种不同的跟腱抬高任务，这些任务被认为对内侧和外侧比目鱼肌室有不同的机械需求。右腿的内侧和外侧比目鱼肌和内侧腓肠肌的高密度肌电图（EMG）信号被分解为单个运动单位的尖峰列车。估计了运动单位累积尖峰列车之间的相干性。相干性分析也针对在所有三个任务中都匹配的运动单位进行了重复。此外，我们计算了一对运动单位尖峰列车之间显著相关的比例。我们观察到，两个比目鱼肌室的运动单位之间的相干性与每个室内部的运动单位之间的相干性相似，而与任务无关。对运动单位对的相关分析证实了这些结果。我们得出结论，支配内侧和外侧后比目鱼肌室的运动单位之间的共同突触传入水平与支配这些室内部的运动单位之间的共同突触传入水平没有差异，这与先前关于手指肌肉的研究结果相反。这表明，单独的后比目鱼肌室没有独立的神经控制。人类比目鱼肌在解剖上可分为四个室。这种分区的功能作用尚不清楚。在这里，我们表明，与手指肌肉的先前发现相反，支配内侧和外侧后比目鱼肌室的运动单位之间的共同突触传入与单个室内部的运动单位之间的共同突触传入相似。我们认为，与其他分隔肌肉的矛盾发现可能是由肌肉 - 肌腱解剖和功能的差异解释的。
