Human Performance Laboratory, University of Calgary Calgary, AB, Canada.
Move Functional, Private Berndorf bei Salzburg, Austria.
Front Physiol. 2014 Jun 17;5:223. doi: 10.3389/fphys.2014.00223. eCollection 2014.
The penniform gastrocnemius muscle contains multiple heads in the proximal regions, and the aponeuroses are attached to the Achilles tendon. The multiple head structure lead to the assumption that different regions of the muscle must be activated compartment wise. The purpose of this study was to compare the correlation and coherence of EMG-currents within and between proximal and distal compartments of the medial gastrocnemius muscle, which reflect underling synchronization of motor units. It was hypothesized and shown that phase inverted signals represent a property that discriminates compartments. However, the phase inverted and non-inverted signals showed values of correlations that were indicative for highly synchronized signals. The correlation increased with the complexity of the task and was higher for the calf rising movement than while balancing in a tiptoe position. Because the muscle fibers do not span the whole length of the muscles, one has to conclude that the MUs were synchronized by synchronizing the various motor nerves. This study shows that it is essential to measure monopolar signals and use non-isometric contractions to observe synchronization of the EMG-signals. One could speculate that compartmental differences can only be observed if more complex movements that generate rotational forces at the knee or ankle are used.
羽状的比目鱼肌在近端区域包含多个头，肌腱膜附于跟腱。这种多头结构导致人们假设肌肉的不同区域必须按节段进行激活。本研究的目的是比较内侧比目鱼肌近端和远端节段之间和内部的肌电图电流的相关性和相干性，这反映了运动单位的潜在同步性。研究假设并表明，相位反转信号代表了区分节段的特性。然而，相位反转和非反转信号的相关性值表明它们是高度同步的信号。相关性随着任务的复杂性而增加，在小腿抬高运动中比在脚尖平衡位置时更高。由于肌肉纤维没有跨越肌肉的整个长度，因此必须得出结论，MU 通过同步各种运动神经来实现同步。这项研究表明，测量单极信号并使用非等长收缩来观察肌电图信号的同步性是至关重要的。人们可以推测，如果使用产生膝关节或踝关节旋转力的更复杂运动，那么只能观察到节段差异。
