Biomechanics of the threshold of balance recovery

在加拿大，跌倒是意外伤害导致住院和永久性残疾的主要原因。然而，直到最近，才出现了大量关于平衡恢复的研究，以应对足够大的姿势扰动，以至于避免摔倒并不总是可能的。不幸的是，这些处于平衡恢复门槛的研究忽略了中年人和侧向和落后的平衡丧失。他们还使用了各种姿势扰动，这使得研究之间的比较变得困难。 在过去的5年里，我们评估了从18岁到85岁的整个年龄范围内平衡恢复能力的下降；提供了进一步的证据，证明姿势扰动的选择不影响平衡恢复的阈值；并在平衡恢复阈值的滑动模型上验证了倒立摆。事实上，使用健康的年轻人、中年人和老年人，我们发现，前倾、侧倾和后倾的平衡恢复能力分别在51岁、61岁和70岁时随年龄呈指数下降。此外，使用健康的年轻人和老年人，我们开发了一种无量纲方法来比较不同姿势扰动的结果。特别是，这种摄动阈值线法将跌倒和恢复区分开来，包括瘦身释放、腰部拉动、行走时腰部拉动和表面平移。最后，我们证明了滑移模型上的倒立摆可以用来从理论上预测给定的姿态摄动是否会导致不可避免的跌落或是否有可能恢复平衡。 在接下来的5年里，我将回答一些关于年龄和失去平衡方向对我们比较姿势扰动的无量纲方法的影响的剩余问题，并开始探索疼痛对平衡恢复阈值的影响，疼痛是跌倒的危险因素。我们的第一个目标是从实验上确定i)最大的前向初始倾斜角度，从那里健康的年轻、中年和老年成年人可以突然释放并仍然使用3个向后表面平移速度的单步来恢复平衡，以及ii)相同的参与者可以突然被拉并且仍然可以使用单步3种行走速度来恢复平衡的最大向后表面平移速度。我们的第二个目标是通过实验确定最大的向前、侧向和向后的最大倾斜角和表面平移速度，健康的年轻人、中年人和老年人可以分别从这些速度中突然释放或拉动，并且仍然使用一步来恢复平衡。我们还将在滑动模型上验证倒立摆对所有这些组合姿势摄动和失去平衡方向的影响。最后，我们的第三个目标是通过实验i)确定在两个不同部位引起的疼痛对健康受试者最大向前初始倾斜角度的影响，以及ii)评估导致这种相互作用的可能的神经生理学机制之一。我们还将探索可能的干预方法，如果该方案被认为对患有慢性疼痛的个人是安全的。 我的工程学方法，使用实验和理论建模以及生物力学和神经生理学方法，将在平衡恢复的门槛上推进知识。从长远来看，这项提议将减少对耗时和危险的实验的需求，可能有助于设计检测甚至防止跌倒的设备，甚至可能有助于秋季诉讼案件。它还可能导致更有效干预计划，以防止第一次损伤性跌倒，从而提高生活质量和功能自主性。

Falls are the leading causes of hospitalizations and permanent disabilities due to unintentional injuries in Canada. However, only recently has a critical mass of studies emerged on balance recovery in response to sufficiently large postural perturbations that avoiding a fall is not always possible. Unfortunately, these studies at the threshold of balance recovery have neglected middle-aged adults and sideways and backward losses of balance. They have also used a variety of postural perturbations which makes comparisons between studies difficult. OVER THE LAST 5 YEARS, we evaluated the decline in balance recovery ability across the whole spectrum of ages from 18 to 85yrs; provided further evidence that the choice of postural perturbation does not affect the threshold of balance recovery; and validated an inverted pendulum on a skid model at the threshold of balance recovery. Indeed, using healthy younger, middle-aged and older adults, we showed that balance recovery ability declines exponentially with age as early as 51, 61 and 70yrs for forward, sideways and backward leans, respectively. Moreover, using healthy younger and older adults, we developed a dimensionless method to compare results from different postural perturbations. In particular, this perturbation threshold line method separates falls from recoveries for lean releases, lean releases with waist pull, waist pulls while walking and surface translations. Finally, we showed that an inverted pendulum on a skid model could be used to theoretically predict if a given postural perturbation will lead to an unavoidable fall or if balance recovery is possible. IN THE NEXT 5 YEARS, I will answer some of the remaining questions regarding the effects of AGE and loss of balance DIRECTION on our dimensionless method to compare postural perturbations, as well as begin to explore the influence of PAIN, a risk factor for falls, on the threshold of balance recovery. OUR 1ST OBJECTIVE is to experimentally determine i) the maximum forward initial lean angles from which healthy YOUNGER, MIDDLE-AGED and OLDER adults can be suddenly released and still recover balance using a single step for 3 backward surface translation velocities, and ii) the maximum backward surface translation velocities from which the same participants can be suddenly pulled and still recover balance using a single step for 3 walking velocities. OUR 2ND OBJECTIVE is to experimentally determine the maximum FORWARD, SIDEWAYS and BACKWARD i) initial lean angles and ii) surface translation velocities from which healthy younger, middle-aged and older adults can be suddenly released or pulled, respectively, and still recover balance using a single step. We will also validate the inverted pendulum on a skid model for all of these combined postural perturbations and loss of balance directions. Finally, OUR 3RD OBJECTIVE is to experimentally i) determine the effect of INDUCED PAIN at 2 different sites on the maximum forward initial lean angles in healthy participants, and ii) evaluate one of the possible neurophysiological mechanisms responsible for this interaction. We will also explore possible intervention methods, if this protocol is deemed safe for individuals with CHRONIC PAIN. My engineering approach, using experiments and theoretical modeling as well as biomechanical and neurophysiological measures, will advance knowledge at the threshold of balance recovery. Long term, this proposal will reduce the need for time consuming and dangerous experiments, could help in designing equipment that detects or even prevents falls, and may even help in fall litigation cases. It could also lead to more efficient intervention programs to prevent that first injurious fall, thereby improving quality of life and functional autonomy.