Maki B E, McIlroy W E, Perry S D
Centre for Studies in Aging, University of Toronto, Canada.
J Biomech. 1996 Mar;29(3):343-53. doi: 10.1016/0021-9290(95)00053-4.
Previous studies of compensatory stepping, in response to postural perturbation, have focussed on forward or backward stepping; however, the ability to step in other directions is of equal functional importance, since the perturbations encountered in daily life may often include a lateral component. The primary objective of this study was to determine how lateral destabilization affects the compensatory stepping response, in terms of: (1) swing-leg selection, (2) preparatory unloading of the swing leg, and (3) spatial and temporal characteristics of the swing trajectory. A novel multi-directional moving platform was used to apply transient perturbations in eight horizontal directions, in 10 healthy young adults. Perturbation magnitude was varied unpredictably over a wide range and subjects were instructed to try not to step, so as to discourage preplanned 'volitional' foot movement. The predominant strategy, seen in 96% of stepping responses to lateral destabilization, was to swing the leg that was unloaded by the perturbation. This strategy allowed a much more rapid foot-lift but required a longer and more complex swing trajectory, compared to responses where the perturbation-loaded leg was swung. When compared to forward and backward steps, the addition of a lateral component to the perturbation led to a 20% (90 ms) reduction in time to foot-off, a 20% (7 cm) increase in step length and a 70% (110 ms) increase in swing duration, on average. The results clearly demonstrate that compensatory stepping responses to non-sagittal perturbations are strongly influenced by biomechanical constraints and affordances that do not affect the forward and backward stepping behaviour that has been studied traditionally. These findings underscore the need to assess postural responses in multiple directions, in order to understand more fully how balance is maintained in the exigencies of everyday life.
以往关于针对姿势扰动的代偿性踏步的研究主要集中在向前或向后踏步；然而，向其他方向踏步的能力同样具有重要的功能意义，因为日常生活中遇到的扰动通常可能包含侧向分量。本研究的主要目的是确定侧向失稳如何影响代偿性踏步反应，具体涉及：（1）摆动腿的选择，（2）摆动腿的准备性卸载，以及（3）摆动轨迹的空间和时间特征。在10名健康的年轻成年人中，使用一种新型的多向移动平台在八个水平方向施加瞬态扰动。扰动幅度在很宽的范围内不可预测地变化，并且受试者被指示尽量不要踏步，以抑制预先计划的“自主”足部运动。在对侧向失稳的96%的踏步反应中观察到的主要策略是摆动被扰动卸载的腿。与摆动受扰动加载腿的反应相比，这种策略允许更快地抬起脚，但需要更长、更复杂的摆动轨迹。与向前和向后踏步相比，在扰动中增加侧向分量平均导致离地时间减少20%（90毫秒），步长增加20%（7厘米），摆动持续时间增加70%（110毫秒）。结果清楚地表明，对非矢状面扰动的代偿性踏步反应受到生物力学限制和可供性的强烈影响，而这些因素并不影响传统上所研究的向前和向后踏步行为。这些发现强调了需要在多个方向评估姿势反应，以便更全面地了解在日常生活的紧急情况下如何维持平衡。
