Cruise Denise R, Chagdes James R, Liddy Joshua J, Rietdyk Shirley, Haddad Jeffrey M, Zelaznik Howard N, Raman Arvind
School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907-2088, United States.
Department of Mechanical and Manufacturing Engineering, Miami University, 650 East High Street, Oxford, OH 45056, United States.
J Biomech. 2017 Jul 26;60:48-56. doi: 10.1016/j.jbiomech.2017.06.018. Epub 2017 Jun 21.
Increased time-delay in the neuromuscular system caused by neurological disorders, concussions, or advancing age is an important factor contributing to balance loss (Chagdes et al., 2013, 2016a,b). We present the design and fabrication of an active balance board system that allows for a systematic study of stiffness and time-delay induced instabilities in standing posture. Although current commercial balance boards allow for variable stiffness, they do not allow for manipulation of time-delay. Having two controllable parameters can more accurately determine the cause of balance deficiencies, and allows us to induce instabilities even in healthy populations. An inverted pendulum model of human posture on such an active balance board predicts that reduced board rotational stiffness destabilizes upright posture through board tipping, and limit cycle oscillations about the upright position emerge as feedback time-delay is increased. We validate these two mechanisms of instability on the designed balance board, showing that rotational stiffness and board time-delay induced the predicted postural instabilities in healthy, young adults. Although current commercial balance boards utilize control of rotational stiffness, real-time control of both stiffness and time-delay on an active balance board is a novel and innovative manipulation to reveal balance deficiencies and potentially improve individualized balance training by targeting multiple dimensions contributing to standing balance.
由神经疾病、脑震荡或年龄增长导致的神经肌肉系统时间延迟增加是导致平衡丧失的一个重要因素（查格德斯等人，2013年、2016年a、b）。我们展示了一种主动平衡板系统的设计与制造，该系统能够对站立姿势中由刚度和时间延迟引起的不稳定性进行系统研究。尽管目前的商业平衡板可以实现可变刚度，但它们无法控制时间延迟。拥有两个可控参数能够更准确地确定平衡缺陷的原因，甚至能让我们在健康人群中诱发不稳定性。在这样一个主动平衡板上，人体姿势的倒立摆模型预测，降低板的旋转刚度会通过板的倾斜使直立姿势失稳，并且随着反馈时间延迟的增加，会出现围绕直立位置的极限环振荡。我们在设计的平衡板上验证了这两种不稳定性机制，表明旋转刚度和板的时间延迟在健康的年轻成年人中诱发了预测的姿势不稳定性。尽管目前的商业平衡板利用旋转刚度控制，但在主动平衡板上对刚度和时间延迟进行实时控制是一种新颖且创新的操作，有助于揭示平衡缺陷，并有可能通过针对影响站立平衡的多个维度来改进个性化平衡训练。
