McIlroy W E, Maki B E
Centre for Studies in Aging, Sunnybrook Health Science Center, University of Toronto, Ontario.
J Gerontol A Biol Sci Med Sci. 1996 Nov;51(6):M289-96. doi: 10.1093/gerona/51a.6.m289.
Recent studies highlight the importance of compensatory stepping to preserve stability, and the spatial and temporal demands placed on the control of this reaction. Age-related changes in the control of stepping could greatly influence the risk of falling. The present study compares, in healthy elderly and young adults, the characteristics of compensatory stepping responses to unpredictable postural perturbations.
A moving platform was used to unpredictably perturb the upright stance of 14 naive, active and mobile subjects (5 aged 22 to 28 and 9 aged 65 to 81). The first 10 randomized trials (5 forward and 5 backward) were evaluated to allow a focus on reactions to relatively novel perturbations. The behavior of the subjects was not constrained. Forceplate and kinematic measures were used to evaluate the responses evoked by the brief (600 msec) platform translation.
Subjects stepped in 98% of the trials. Although the elderly were less likely to execute a lateral anticipatory postural adjustment prior to foot-lift, the onset of swing-leg unloading tended to begin at the same time in the two age groups. There was remarkable similarity between the young and elderly in many other characteristics of the first step of the response. In spite of this similarity, the elderly subjects were twice as likely to take additional steps to regain stability (63% of trials for elderly). Moreover, in elderly subjects, the additional steps were often directed so as to preserve lateral stability, whereas the young rarely showed this tendency.
Given the functional significance of base-of-support changes as a strategy for preserving stability and the age-related differences presently revealed, assessment of the capacity to preserve stability against unpredictable perturbation, and specific measures such as the occurrence or placement of multiple steps, may prove to be a significant predictor of falling risk and an important outcome in evaluating or developing intervention strategies to prevent falls.
近期研究强调了代偿性迈步对维持稳定性的重要性，以及对这种反应控制所提出的空间和时间要求。与年龄相关的迈步控制变化可能会极大地影响跌倒风险。本研究比较了健康老年人和年轻人对不可预测的姿势扰动的代偿性迈步反应特征。
使用移动平台对14名未经训练、活跃且行动自如的受试者（5名年龄在22至28岁之间，9名年龄在65至81岁之间）的直立姿势进行不可预测扰动。对前10次随机试验（5次向前和5次向后）进行评估，以便重点关注对相对新颖扰动的反应。受试者的行为不受限制。使用测力台和运动学测量方法来评估由短暂（600毫秒）平台平移所诱发的反应。
在98%的试验中受试者会迈步。尽管老年人在抬脚前进行侧向预期姿势调整的可能性较小，但摆动腿卸载的起始时间在两个年龄组中趋于同时开始。在反应的第一步的许多其他特征方面，年轻人和老年人之间存在显著相似性。尽管有这种相似性，但老年受试者采取额外步骤以恢复稳定性的可能性是年轻人的两倍（老年受试者在63%的试验中如此）。此外，在老年受试者中，额外步骤通常是为了保持侧向稳定性而进行的，而年轻人很少表现出这种趋势。
鉴于支撑面变化作为维持稳定性策略的功能重要性以及目前所揭示的与年龄相关的差异，评估针对不可预测扰动维持稳定性的能力以及诸如多步的发生或位置等具体指标，可能被证明是跌倒风险的重要预测指标，也是评估或制定预防跌倒干预策略的重要结果。
