Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
School of Health and Sport Sciences, Chukyo University, 101-2 Yagoto Honmachi, Showa-ku, Nagoya-shi, Aichi, Japan.
Gait Posture. 2022 May;94:230-235. doi: 10.1016/j.gaitpost.2021.04.006. Epub 2021 Apr 6.
Modular organization in muscular control is generally specified as synergistic muscle groups that are hierarchically organized. There are conflicting perspectives regarding modular organization for regulation of walking speeds, with regard to whether modular organization is relatively consistent across walking speeds. This conflict might arise from different stride time (time for one stride) and stride length combinations for achieving the same walking speed.
Does the regulation of the modular organization depend on stride time and stride length (stride time-length) combinations?
Ten healthy men walked at a moderate speed (nondimensional speed = 0.4) on a treadmill at five different stride time-length combinations (very short, short, preferred, long, and very long). Surface electromyograms from 16 muscles in the trunk and lower limb were recorded. The modular organization was modeled as muscle synergies, which represent groups of synchronously activated muscles. Muscle synergies were extracted using a decomposition technique. The number of synergies and their activation durations were analyzed.
The number of synergies was consistent in the preferred and quasi-preferred condition (median: 4.5 [short], 4.5 [preferred], 5 [long]), while it varied in the extreme condition (median: 4 [very short] and 6 [very long]; 0.02 ≤ p ≤ 0.09). Gait parameters (stride time, stride length, stance time, swing time, and double stance time) were significantly different for preferred and quasi-preferred conditions (p < 0.03).
Our results provide additional insights on the flexibility of modular control during walking, namely that the number of synergies or activations are fine-tuned even within one walking speed. Our finding implies that a variety of walking patterns can be achieved by consistent synergies except for extreme walking patterns.
肌肉控制的模块化组织通常被指定为具有层次结构的协同肌肉群。关于调节步行速度的模块化组织存在相互矛盾的观点，即模块化组织是否在不同的步行速度下相对一致。这种冲突可能是由于达到相同步行速度的不同步幅时间（一步的时间）和步幅长度组合引起的。
模块化组织的调节是否取决于步幅时间和步幅长度（步幅时间-长度）组合？
10 名健康男性在跑步机上以中等速度（无量纲速度=0.4）行走，在五个不同的步幅时间-长度组合（非常短、短、首选、长和非常长）下进行。记录来自躯干和下肢 16 块肌肉的表面肌电图。模块化组织被建模为肌肉协同作用，代表同步激活的肌肉群。使用分解技术提取肌肉协同作用。分析协同作用的数量及其激活持续时间。
在首选和准首选条件下，协同作用的数量是一致的（中位数：4.5[短]、4.5[首选]、5[长]），而在极端条件下则不同（中位数：4[非常短]和 6[非常长]；0.02≤p≤0.09）。首选和准首选条件下的步态参数（步幅时间、步幅长度、支撑时间、摆动时间和双支撑时间）存在显著差异（p<0.03）。
我们的结果提供了关于行走过程中模块化控制灵活性的更多见解，即即使在一个步行速度下，协同作用的数量或激活也可以进行微调。我们的发现意味着，除了极端的行走模式外，通过一致的协同作用可以实现多种行走模式。
