Dingwell J B, Cusumano J P, Sternad D, Cavanagh P R
Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Room 1406, 345 E. Superior Street, IL 60611, USA.
J Biomech. 2000 Oct;33(10):1269-77. doi: 10.1016/s0021-9290(00)00092-0.
Patients with diabetic peripheral neuropathy are significantly more likely to fall while walking than subjects with intact sensation. While it has been suggested that these patients walk slower to improve locomotor stability, slower speeds are also associated with increased locomotor variability, and increased variability has traditionally been equated with loss of stability. If the latter were true, this would suggest that slowing down, as a locomotor control strategy, should be completely antithetical to the goal of maintaining stability. The present study resolves these seemingly paradoxical findings by using methods from nonlinear time series analysis to directly quantify the sensitivity of the locomotor system to local perturbations that are manifested as natural kinematic variability. Fourteen patients with severe peripheral neuropathy and 12 gender-, age-, height-, and weight-matched non-diabetic controls participated. Sagittal plane angles of the right hip, knee, and ankle joints and tri-axial accelerations of the trunk were measured during 10 min of continuous overground walking at self-selected speeds. Maximum finite-time Lyapunov exponents were computed for each time series to quantify the local dynamic stability of these movements. Neuropathic patients exhibited slower walking speeds and better local dynamic stability of upper body movements in the horizontal plane than did control subjects. The differences in local dynamic stability were significantly predicted by differences in walking speed, but not by differences in sensory status. These results support the hypothesis that reductions in walking speed are a compensatory strategy used by neuropathic patients to maintain dynamic stability of the upper body during level walking.
与感觉正常的受试者相比，糖尿病周围神经病变患者在行走时摔倒的可能性要大得多。虽然有人认为这些患者会走得更慢以提高运动稳定性，但较慢的速度也与运动变异性增加有关，而传统上认为变异性增加等同于稳定性丧失。如果后者是真的，这将表明，作为一种运动控制策略，放慢速度应该与保持稳定性的目标完全背道而驰。本研究通过使用非线性时间序列分析方法，直接量化运动系统对表现为自然运动学变异性的局部扰动的敏感性，解决了这些看似矛盾的发现。14名患有严重周围神经病变的患者和12名性别、年龄、身高和体重匹配的非糖尿病对照者参与了研究。在以自选速度进行10分钟的连续地面行走过程中，测量了右髋、膝和踝关节的矢状面角度以及躯干的三轴加速度。计算每个时间序列的最大有限时间李雅普诺夫指数，以量化这些运动的局部动态稳定性。与对照受试者相比，神经病变患者的行走速度较慢，上半身在水平面运动的局部动态稳定性更好。局部动态稳定性的差异由行走速度的差异显著预测，而不是由感觉状态的差异预测。这些结果支持了这样一种假设，即行走速度降低是神经病变患者在平地上行走时用来维持上半身动态稳定性的一种补偿策略。
