Hubbuch Jill E, Bennett Blake W, Dean Jesse C
Division of Physical Therapy, College of Health Professions, Medical University of South Carolina, Charleston, SC, USA.
Division of Physical Therapy, College of Health Professions, Medical University of South Carolina, Charleston, SC, USA; Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA.
J Biomech. 2015 Aug 20;48(11):2925-31. doi: 10.1016/j.jbiomech.2015.04.024. Epub 2015 Apr 23.
Humans generally prefer gait patterns with a low metabolic cost, but it is unclear how such patterns are chosen. We have previously proposed that humans may use proprioceptive feedback to identify economical movement patterns. The purpose of the present experiments was to investigate the role of plantarflexor proprioception in the adaptation toward an economical gait pattern. To disrupt proprioception in some trials, we applied noisy vibration (randomly varying between 40-120Hz) over the bilateral Achilles tendons while participants stood quietly or walked on a treadmill. For all 10min walking trials, the treadmill surface was initially level before slowly increasing to a 2.5% incline midway through the trial without participant knowledge. During standing posture, noisy vibration increased sway, indicating decreased proprioception accuracy. While walking on a level surface, vibration did not significantly influence stride period or metabolic rate. However, vibration had clear effects for the first 2-3min after the incline increase; vibration caused participants to walk with shorter stride periods, reduced medial gastrocnemius (MG) activity during mid-stance (30-65% stance), and increased MG activity during late-stance (65-100% stance). Over time, these metrics gradually converged toward the gait pattern without vibration. Likely as a result of this delayed adaptation to the new mechanical context, the metabolic rate when walking uphill was significantly higher in the presence of noisy vibration. These results may be explained by the disruption of proprioception preventing rapid identification of muscle activation patterns which allow the muscles to operate under favorable mechanical conditions with low metabolic demand.
人类通常更喜欢代谢成本较低的步态模式，但尚不清楚这种模式是如何被选择的。我们之前曾提出，人类可能会利用本体感觉反馈来识别经济的运动模式。本实验的目的是研究跖屈肌本体感觉在向经济步态模式适应过程中的作用。为了在某些试验中干扰本体感觉，我们在参与者安静站立或在跑步机上行走时，在双侧跟腱上施加噪声振动（在40 - 120Hz之间随机变化）。在所有10分钟的步行试验中，跑步机表面最初是水平的，在试验进行到一半时，在参与者不知情的情况下缓慢增加到2.5%的坡度。在站立姿势期间，噪声振动增加了摇摆，表明本体感觉准确性下降。在水平表面上行走时，振动对步幅周期或代谢率没有显著影响。然而，在坡度增加后的最初2 - 3分钟内，振动有明显影响；振动导致参与者步幅周期变短，在站立中期（站立的30 - 65%）腓肠肌内侧（MG）活动减少，而在站立后期（站立的65 - 100%）MG活动增加。随着时间的推移，这些指标逐渐趋向于无振动时的步态模式。可能是由于对新的力学环境的这种延迟适应，在存在噪声振动的情况下，上坡行走时的代谢率显著更高。这些结果可能是由于本体感觉的破坏阻止了对肌肉激活模式的快速识别，而这种模式能使肌肉在有利的力学条件下以低代谢需求运作。
