Sano Tsubasa, Takeda Misaki, Nambu Isao, Wada Yasuhiro
Annu Int Conf IEEE Eng Med Biol Soc. 2020 Jul;2020:4803-4806. doi: 10.1109/EMBC44109.2020.9176540.
Muscle synergy is the theory that movements are controlled by a module of coordinated combined muscles. This theory is thought to solve the degrees-of-freedom problem in the musculoskeletal system. Previous studies have investigated the robustness of muscle synergies under conditions such as varying speeds and required degrees of accuracy. One of the principles of human movement is that when movement becomes faster, spatial accuracy is reduced. This is called the "speed-accuracy trade-off" (SAT), and many models have been proposed to explain this phenomenon. Studies on muscle synergies have shown that muscle synergy modules are robust against changes in speed; however, the relationship between SAT and motor control by muscle synergies remains unclear. Therefore, we investigated the relationship between changes in spatial accuracy and changes in speed and muscle synergies from measured behavioral data and surface electromyography. This was achieved by performing an isometric contraction task in which subjects exerted a horizontal force with various movement speeds. The results showed that the module structures of muscle synergies were robust against speed changes, and that the neural commands to muscle synergies changed in response to speed changes. In addition, changes in spatial accuracy with variations in speed tended to increase when movement was performed with a single muscle synergy. These results suggest that the number of muscle synergies used for movement may affect movement accuracy.Clinical Relevance-The results of this study suggest that the number of muscle synergies used for movement affects spatial accuracy.
肌肉协同作用理论认为，运动是由一组协调的联合肌肉控制的。该理论被认为可以解决肌肉骨骼系统中的自由度问题。先前的研究已经在诸如不同速度和所需精度等条件下研究了肌肉协同作用的稳健性。人体运动的一个原则是，当运动速度加快时，空间精度会降低。这被称为“速度-精度权衡”（SAT），并且已经提出了许多模型来解释这种现象。关于肌肉协同作用的研究表明，肌肉协同作用模块对速度变化具有稳健性；然而，SAT与肌肉协同作用的运动控制之间的关系仍不清楚。因此，我们从测量的行为数据和表面肌电图中研究了空间精度变化、速度变化与肌肉协同作用之间的关系。这是通过执行一项等长收缩任务来实现的，在该任务中，受试者以各种运动速度施加水平力。结果表明，肌肉协同作用的模块结构对速度变化具有稳健性，并且对肌肉协同作用的神经指令会随着速度变化而改变。此外，当用单一肌肉协同作用进行运动时，随着速度变化的空间精度变化往往会增加。这些结果表明，用于运动的肌肉协同作用的数量可能会影响运动精度。临床相关性——本研究结果表明，用于运动的肌肉协同作用的数量会影响空间精度。
