Muscle synergies during shifts of the center of pressure by standing persons: identification of muscle modes
Muscle synergies during shifts of the center of pressure by standing persons: identification of muscle modes
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DOI：
10.1007/s00422-003-0419-5
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发表时间：
2003-08-01
影响因子：
1.9
通讯作者：
Latash, ML
中科院分区：
文献类型：
--
作者：
Krishnamoorthy, V;Goodman, S;Latash, ML
当一个站立的人做一个使重心转移的动作时，姿势肌肉的活动就会调整以保持平衡。我们假设这样的调整是由一小组中心变量控制的，而每个变量都会引起一组体位肌肉活动的变化。本研究的目的是识别这些肌肉群（肌肉模式或m -模式），并在不同任务和受试者之间进行比较。四项任务要求受试者在释放负荷之前从伸展臂上释放负荷，导致压力中心（COP）转移。第五项任务要求缔约方大会通过自愿影响进行明确的转变。将身体一侧11块体位肌肉的肌电图活动在与COP转换早期阶段相对应的100毫秒间隔内进行整合，并在每个任务的多次重复中对这种整合的肌电图活动进行主成分（PC）分析。三个pc被识别并与“向后推m模式”，“向前推m模式”和“混合m模式”相关联。跨任务和跨对象的PC向量聚类分析证实了独特的前推和后推肌群的存在。PC向量也在不同的任务和科目之间进行比较，使用余弦作为向量对之间共线性的度量。总的来说，m模式在任务和被试中都是相似的。我们得出的结论是，COP的变化，无论是隐性的还是显性的，都是由一小组中心变量控制的，这些中心变量与强健体位肌亚群的活动变化有关。这些结果可用于将来分析与姿势任务相关的肌肉协同作用。
When a standing person performs a movement such that the center of gravity shifts, the activity of postural muscles adjusts to keep the balance. We assume that such adjustments are controlled using a small set of central variables, while each variable induces changes in the activity of a subgroup of postural muscles. The purpose of this study has been to identify such muscle groups (muscle modes or M-modes) and compare them across tasks and subjects. Four tasks required the subjects to release a load from extended arms leading to a center of pressure (COP) shift prior to the load release. The fifth task required an explicit COP shift by voluntary sway. Electromyographic activity of 11 postural muscles on one side of the body was integrated over a 100-ms interval corresponding to the early stage of the COP shift, and this integrated EMG activity was subjected to a principal component (PC) analysis across multiple repetitions of each task. Three PCs were identified and associated with a "push-back M-mode," a "push-forward M-mode," and a "mixed M-mode." Cluster analysis of the PC vectors across tasks and across subjects confirmed the existence of distinctive push-forward and push-back muscle groups. PC vectors were also compared across tasks and across subjects using cosines as a measure-of colinearity between pairs of vectors. In general, M-modes were similar across both tasks and subjects. We conclude that shifts of the COP, whether implicit or explicit, are controlled using a small set of central variables associated with changes in the activity of robust subsets of postural muscles. These results can be used for future analysis of muscle synergies associated with postural tasks.