在步幅极大时，顺应性行走在代谢方面似乎具有优势。

Kim Jaehoon, Bertram John E A

Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada.

Department of Cell Biology and Anatomy, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada.

Gait Posture. 2018 Jul;64:84-89. doi: 10.1016/j.gaitpost.2018.05.020. Epub 2018 May 19.

BACKGROUND

Humans alter gait in response to unusual gait circumstances to accomplish the task of walking. For instance, subjects spontaneously increase leg compliance at a step length threshold as step length increases. Here we test the hypothesis that this transition occurs based on the level of energy expenditure, where compliant walking becomes less energetically demanding at long step lengths.

RESEARCH QUESTION

To map and compare the metabolic cost of normal and compliant walking as step length increases.

METHODS

10 healthy individuals walked on a treadmill using progressively increasing step lengths (100%, 120%, 140% and 160% of preferred step length), in both normal and compliant leg walking as energy expenditure was recorded via indirect calorimetry. Leg compliance was controlled by lowering the center-of-mass trajectory during stance, forcing the leg to flex and extend as the body moved over the foot contact.

RESULTS

For normal step lengths, compliant leg walking was more costly than normal walking gait, but compliant leg walking energetic cost did not increase as rapidly for longer step lengths. This led to an intersection between normal and compliant walking cost curves at 114% relative step length (regression analysis; r = 0.92 for normal walking; r = 0.65 for compliant walking).

SIGNIFICANCE

Compliant leg walking is less energetically demanding at longer step lengths where a spontaneous shift to compliant walking has been observed, suggesting the human motor control system is sensitive to energetic requirements and will employ alternate movement patterns if advantageous strategies are available. The transition could be attributed to the interplay between (i) leg work controlling body travel during single stance and (ii) leg work to control energy loss in the step-to-step transition. Compliant leg walking requires more stance leg work at normal step lengths, but involves less energy loss at the step-to-step transition for very long steps.

背景

人类会根据异常的步态情况改变步态以完成行走任务。例如，随着步长增加，受试者在步长阈值时会自发增加腿部顺应性。在此，我们测试这样一个假设，即这种转变是基于能量消耗水平发生的，在长步长时顺应性行走的能量需求较低。

研究问题

绘制并比较随着步长增加正常行走和顺应性行走的代谢成本。

方法

10名健康个体在跑步机上行走，步长逐渐增加（为偏好步长的100%、120%、140%和160%），分别采用正常腿部行走和顺应性腿部行走方式，同时通过间接量热法记录能量消耗。通过在站立期降低质心轨迹来控制腿部顺应性，当身体在足部接触上方移动时迫使腿部弯曲和伸展。

结果

对于正常步长，顺应性腿部行走比正常行走步态成本更高，但对于更长步长，顺应性腿部行走的能量成本增加得没有那么快。这导致正常行走和顺应性行走成本曲线在相对步长114%处相交（回归分析；正常行走r = 0.92；顺应性行走r = 0.65）。

意义

在观察到自发转变为顺应性行走的长步长处，顺应性腿部行走的能量需求较低，这表明人类运动控制系统对能量需求敏感，如果有有利策略可用，将采用替代运动模式。这种转变可能归因于以下两者之间的相互作用：（i）在单支撑期控制身体移动的腿部功，以及（ii）在步间转换中控制能量损失的腿部功。顺应性腿部行走在正常步长时需要更多的支撑腿功，但在非常长的步长的步间转换中能量损失较少。