Fettrow Tyler, Reimann Hendrik, Grenet David, Crenshaw Jeremy, Higginson Jill, Jeka John
Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, United States.
Department of Mechanical Engineering, University of Delaware, Newark, DE, United States.
Front Sports Act Living. 2019 Oct 1;1:40. doi: 10.3389/fspor.2019.00040. eCollection 2019.
We have previously identified three balance mechanisms that young healthy adults use to maintain balance while walking. The three mechanisms are: (1) The lateral ankle mechanism, an active modulation of ankle inversion/eversion in stance; (2) The foot placement mechanism, an active shift of the swing foot placement; and (3) The push-off mechanism, an active modulation of the ankle plantarflexion angle during double stance. Here we seek to determine whether there are changes in neural control of balance when walking at different cadences and speeds. Twenty-one healthy young adults walked on a self-paced treadmill while immersed in a 3D virtual reality cave, and periodically received balance perturbations (bipolar galvanic vestibular stimulation) eliciting a perceived fall to the side. Subjects were instructed to match two cadences specified by a metronome, 110 bpm () and 80 bpm (), which in this experiment, led to faster and slower gait speeds, respectively. The results indicate that subjects altered the use of the balance mechanisms at different cadences. The lateral ankle mechanism was used more in the condition, while the foot placement mechanism was used more in the condition. There was no difference in the use of the push-off mechanism between cadence conditions. These results suggest that neural control of balance is altered when gait characteristics, such as cadence change, suggesting a flexible balance response that is sensitive to the constraints of the gait cycle. We speculate that the use of the balance mechanisms may be a factor resulting in well-known characteristics of gait in populations with compromised balance control, such as slower gait speed in older adults or higher cadence in people with Parkinson's disease.
我们之前已经确定了年轻健康成年人在行走时用于维持平衡的三种平衡机制。这三种机制分别是：（1）外侧踝关节机制，即站立时对踝关节内翻/外翻的主动调节；（2）足部放置机制，即摆动足放置的主动移位；（3）蹬离机制，即双支撑期踝关节跖屈角度的主动调节。在此，我们试图确定在不同步频和速度行走时，平衡的神经控制是否存在变化。21名健康的年轻成年人在自行调节速度的跑步机上行走，同时置身于一个3D虚拟现实洞穴中，并定期接受平衡扰动（双极电刺激前庭），引发向一侧的感知性跌倒。受试者被要求匹配节拍器指定的两种步频，110次/分钟（）和80次/分钟（），在本实验中，这分别导致更快和更慢的步态速度。结果表明，受试者在不同步频下改变了平衡机制的使用。在步频为 时更多地使用外侧踝关节机制，而在步频为 时更多地使用足部放置机制。在不同步频条件下，蹬离机制的使用没有差异。这些结果表明，当步态特征（如步频变化）改变时，平衡的神经控制也会改变，这表明存在一种灵活的平衡反应，对步态周期的限制很敏感。我们推测，平衡机制的使用可能是导致平衡控制受损人群中众所周知的步态特征的一个因素，比如老年人步态速度较慢或帕金森病患者步频较高。
