Maki B E, Perry S D, Norrie R G, McIlroy W E
Centre for Studies in Aging, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario, Canada.
J Gerontol A Biol Sci Med Sci. 1999 Jun;54(6):M281-7. doi: 10.1093/gerona/54.6.m281.
One of the more pervasive effects of aging is loss of cutaneous sensation, which appears to correlate with impaired postural control and increased risk of falling. This study examined the potential for compensating for the destabilizing effects of reduced cutaneous sensitivity by placing a raised edge underneath the perimeter of the plantar foot surface, so as to facilitate sensation from the stability boundaries of the base of support.
The main experiment involved 14 healthy older adults (aged 65-73) selected because they were known, from a previous study, to have moderate plantar cutaneous insensitivity. We also report results of an initial experiment involving 7 healthy young adults (aged 23-31). In both experiments, we studied effects of the plantar facilitation on control of rapid stepping reactions evoked by unpredictable postural perturbation, applied via sudden platform movement in forward, backward, and lateral directions. We also studied effects on "feet-in-place" responses evoked by continuous pseudorandom platform motion in mediolateral and anteroposterior directions. Subjects were blindfolded in all tests.
Plantar facilitation reduced the incidence of "extra" limb movements, beyond the initial step, during forward-step reactions in the older adults. There also appeared to be an improved ability to control feet-in-place reactions: young subjects were better able to recover balance without stepping when falling backward (given instructions to "try not to step"), and both young and older subjects reduced the extent to which the center of foot pressure approached the posterior foot boundary during continuous anteroposterior platform motion.
This study provides evidence that mechanical facilitation of sensation from the boundaries of the plantar surface of the foot can improve the efficacy of certain types of stabilizing reactions evoked by unpredictable postural perturbation. The results may be directly transferable to the design of special footwear insoles to reduce instability and risk of falling in older adults.
衰老较为普遍的影响之一是皮肤感觉丧失，这似乎与姿势控制受损和跌倒风险增加相关。本研究通过在足底表面周边下方放置一个凸起边缘，来检验补偿皮肤敏感性降低的不稳定效应的可能性，以便从支撑面底部的稳定边界促进感觉。
主要实验涉及14名健康老年人（年龄65 - 73岁），选择他们是因为在之前的一项研究中已知他们存在中度足底皮肤感觉迟钝。我们还报告了一项涉及7名健康年轻人（年龄23 - 31岁）的初始实验结果。在两个实验中，我们研究了足底促进对由不可预测的姿势扰动诱发的快速踏步反应控制的影响，姿势扰动通过平台在向前、向后和侧向方向的突然移动来施加。我们还研究了对由平台在内外侧和前后方向的连续伪随机运动诱发的“原地踏步”反应的影响。在所有测试中，受试者均被蒙上眼睛。
在老年人向前踏步反应期间，足底促进减少了初始踏步之外“额外”肢体运动的发生率。似乎在控制原地踏步反应方面也有能力改善：年轻受试者在向后跌倒时（在接到“尽量不要迈步”的指令时）更有能力在不迈步的情况下恢复平衡，并且年轻和老年受试者在平台连续前后运动期间均减少了足底压力中心接近后足边界的程度。
本研究提供了证据表明，对足底表面边界感觉的机械促进可以提高由不可预测的姿势扰动诱发的某些类型稳定反应的功效。这些结果可能可直接应用于特殊鞋垫的设计，以减少老年人的不稳定性和跌倒风险。
