Faculty of Integrated Human Studies, Kyoto University, Kyoto, Japan.
J Electromyogr Kinesiol. 2013 Apr;23(2):430-7. doi: 10.1016/j.jelekin.2012.11.003. Epub 2012 Dec 5.
To examine the muscle synergies of multi-directional postural control, we calculated the target-directed variance fraction (η) and net action direction of each muscle using the electromyogram-weighted averaging (EWA) method. Subjects stood barefoot on a force platform and maintained their posture by producing a center of pressure (COP) in twelve target directions. Surface electromyograms were recorded from 6 right-sided muscles: tibialis anterior (TA), soleus (SOL), lateral gastrocnemius (LG), medial gastrocnemius (MG), fibularis longus (FL), and gluteus medius (GM). η was calculated from COP with duration of 20-s, during which the COP was relatively constant. The EWA method was applied to the EMG and the two COP components to estimate the net action direction of each muscle. The results showed that η values in all directions did not cross the 0.8 threshold. This suggests that human postural control is achieved by synergistic co-activation. The EWA revealed that the net action directions of TA, SOL, LG, MG, and GM were 277.6°, 71.1°, 87.7°, 94.0°, and 2.2°, respectively. This suggests that postural maintenance by muscle synergy can be attributed to the relevant muscles having various action directions. These results demonstrate that muscle synergies can be investigated using COP fluctuations.
为了研究多向姿势控制的肌肉协同作用，我们使用肌电图加权平均（EWA）法计算了每个肌肉的目标定向方差分数（η）和净作用方向。受试者赤脚站在力台上，通过在十二个目标方向上产生压力中心（COP）来维持姿势。从 6 个右侧肌肉记录表面肌电图：胫骨前肌（TA）、比目鱼肌（SOL）、腓肠外侧肌（LG）、腓肠内侧肌（MG）、腓骨长肌（FL）和臀中肌（GM）。η 是从持续 20 秒的 COP 计算得出的，在此期间 COP 相对稳定。EWA 方法应用于肌电图和两个 COP 分量，以估计每个肌肉的净作用方向。结果表明，所有方向的η值都没有超过 0.8 的阈值。这表明人体姿势控制是通过协同的共同激活来实现的。EWA 显示 TA、SOL、LG、MG 和 GM 的净作用方向分别为 277.6°、71.1°、87.7°、94.0°和 2.2°。这表明肌肉协同作用可以维持姿势归因于相关肌肉具有各种作用方向。这些结果表明可以使用 COP 波动来研究肌肉协同作用。
