LIMB COLLAPSE AND FALLS AMONG ELDERLY

保护性步进是一种用于平衡恢复的常见反应。然而，保护性步进失败的潜在机制在很大程度上尚未被探索和未知。我们正在开拓一项工作，专注于保护步进失败的确切原因。我们希望我们的研究能为未来基于特异性原则的物理康复干预铺平道路。我们将首先证明肢体塌陷是保护性行走失败的主要原因，而年龄和性别是肢体塌陷后成功恢复平衡的关键决定因素。我们将检验以下假设：所有受试者在日常活动中意外滑倒时都会发生肢体塌陷；与年轻人（22-45岁）和男性相比，更多的老年人（65-80岁）和女性成年人将无法从肢体塌陷中恢复过来。为了理解为什么一些老年受试者能够从肢体塌陷中恢复，而另一些却不能，我们接下来将确定肢体塌陷的生物力学原因。我们将测试假设肢体塌陷是不可避免的，在一些研究生科目，因为支撑膝盖（而不是髋关节或踝关节）未能产生扭矩达到恢复阈值，而且这个阈值是可预测的。为了找到具体的方法来加强个人对肢体塌陷的抵抗力，我们将研究从肢体塌陷中恢复的神经肌肉机制。我们将测试这样的假设，即伸展力矩不足是由于长时间的反射性介导的抑制，类似于惊吓或其他相关反应的某些成分，而不是由于在质心垂直下降的关键时间窗期间前馈编程的失败。我们的长期目标是发展康复计划，以促进和加强老年人自身对由于肢体塌陷而导致的灾难性跌倒的抵抗力。其结果将是降低医疗保健费用和不必要的伤害，这些伤害目前降低了灾难性跌倒受害者的行动能力和生活质量。

Protective stepping is a common response used for balance recovery. Nevertheless, the mechanisms underlying situations where protective stepping fails are largely unexplored and unknown. We are pioneering a line of work that focuses on the precise causes for failure in protective stepping. We expect our research to pave the way for future interventions based on the specificity principle in physical rehabilitation. We will first demonstrate that limb collapse is the major cause for failure in protective stepping, and that age and gender are critical determinants in successful attempts to regain balance after limb collapse. We will test the hypotheses that limb collapse will occur in all subjects during unexpected slipping in the execution of a daily activity, and that a greater number of older adults (ages 65-80 years) and female adults will not be able to recover from limb collapse than young adults (ages 22-45 years) and male adults. In order to understand why some older subjects are able to recover from limb collapse while other fail to do so, we will next determine the biomechanical causes for limb collapse. We will test the hypotheses that limb collapse is inevitable in some graduate subjects because the supporting knee (instead of hip or ankle) has failed to generate torques to reach threshold value for recovery, and furthermore that this threshold is predictable. In order to find the specific means to strengthen an individual's resistance to limb collapse, we will then examine the neuromuscular mechanisms for recovery from limb collapse. We will test the hypotheses that insufficient extension torques result from a prolonged, reflexively mediated inhibition similar to some component of startle or other related responses, rather than from a failure of feed-forward programming during the critical time-window of center of mass vertical descent. Our long-term goal is to develop rehabilitation programs that will facilitate and fortify elderly individuals' own resistance to catastrophic falls due to limb collapse. The results will be a reduction in both costs of health care and in unnecessary injury that currently lowers the mobility and the quality of life of victims of catastrophic falls.