Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, 90033, USA.
Sci Rep. 2017 Aug 9;7(1):7682. doi: 10.1038/s41598-017-08147-y.
The theory that the sensorimotor system minimizes energetic cost during locomotion has long been supported by both computational models and empirical studies. However, it has yet to be determined if the behavior to which people converge when exposed to a novel perturbation during locomotion is also energetically optimal. We address this issue in the context of adaptation to walking on a split-belt treadmill, which can impose a left-right asymmetry in step lengths. In response to this asymmetry, participants gradually adjust their foot placement to adopt steps of equal length. Here, we characterized metabolic, mechanical, and perceptual estimates of energetic cost associated with a range of asymmetries to determine whether symmetry is the energetically optimal strategy for walking on a split-belt treadmill. We found that taking steps of equal length did not minimize metabolic cost or mechanical cost. In addition, perceptual estimates of cost were not sensitive to changes in asymmetry. However, symmetry was identified as the optimal strategy when energetic cost was estimated from a composite metric that combined both metabolic and mechanical costs. These results suggest that adaptation may arise from optimization of a composite estimate of effort derived from feedback about the interaction between the body and environment.
运动感知系统在运动过程中最小化能量消耗的理论长期以来一直得到计算模型和实证研究的支持。然而，人们在运动过程中受到新的干扰时所表现出的行为是否也是能量最优的，这一点尚未确定。我们在适应分带跑步机行走的背景下解决了这个问题，分带跑步机可以在步长上产生左右不对称。为了应对这种不对称，参与者逐渐调整他们的脚步位置，以采用等长的步幅。在这里，我们描述了与一系列不对称相关的能量消耗的代谢、力学和感知估计，以确定在分带跑步机上行走时，对称是否是能量最优的策略。我们发现，采用等长步幅并不能使代谢成本或机械成本最小化。此外，成本的感知估计对不对称的变化不敏感。然而，当从综合代谢和机械成本的复合指标来估计能量成本时，对称被确定为最优策略。这些结果表明，适应可能源于对来自身体与环境相互作用的反馈的努力的综合估计的优化。
