Kibushi Benio, Moritani Toshio, Kouzaki Motoki
Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonamatsu, Sakyo-ku, Kyoto, Kyoto, 606-8501, Japan.
Research Fellow of the Japan Society for the Promotion of Science, Kojimachi Business Center Building, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo, Japan.
Exp Brain Res. 2019 Jan;237(1):257-271. doi: 10.1007/s00221-018-5422-0. Epub 2018 Nov 2.
For the regulation of walking speed, the central nervous system must select appropriate combinations of stride time and stride length (stride time-length combinations) and coordinate many joints or segments in the whole body. However, humans achieve both appropriate selection of stride time-length combinations and effortless coordination of joints or segments. Although this selection of stride time-length combination has been explained by minimized energy cost, it may also be explained by the stability of kinematic coordination. Therefore, we investigated the stability of kinematic coordination during walking across various stride time-length combinations. Whole body kinematic coordination was quantified as the kinematic synergies that represents the groups of simultaneously move segments (intersegmental coordination) and their activation patterns (temporal coordination). In addition, the maximum Lyapunov exponents were utilized to evaluate local dynamic stability. We calculated the maximum Lyapunov exponents in temporal coordination of kinematic synergies across various stride time-length combinations. The results showed that the maximum Lyapunov exponents of temporal coordination depended on stride time-length combinations. Moreover, the maximum Lyapunov exponents were high at fast walking speeds and very short stride length conditions. This result implies that fast walking speeds and very short stride length were associated with lower local dynamic stability of temporal coordination. We concluded that fast walking is associated with lower local dynamic stability of temporal coordination of kinematic synergies.
为了调节步行速度，中枢神经系统必须选择合适的步幅时间和步幅长度组合（步幅时间 - 长度组合），并协调全身的多个关节或节段。然而，人类既能实现步幅时间 - 长度组合的恰当选择，又能毫不费力地协调关节或节段。虽然步幅时间 - 长度组合的这种选择已通过最小化能量消耗来解释，但也可能由运动学协调的稳定性来解释。因此，我们研究了在各种步幅时间 - 长度组合下步行过程中运动学协调的稳定性。全身运动学协调被量化为运动协同，它代表同时运动节段的组（节段间协调）及其激活模式（时间协调）。此外，利用最大李雅普诺夫指数来评估局部动态稳定性。我们计算了在各种步幅时间 - 长度组合下运动协同时间协调中的最大李雅普诺夫指数。结果表明，时间协调的最大李雅普诺夫指数取决于步幅时间 - 长度组合。而且，在快走速度和非常短的步幅长度条件下，最大李雅普诺夫指数较高。这一结果意味着快走速度和非常短的步幅长度与时间协调的较低局部动态稳定性相关。我们得出结论，快走与运动协同时间协调的较低局部动态稳定性相关。
