Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE 68182, USA.
Division of Physical Therapy Education, University of Nebraska Medical Center, Omaha, NE 68198, USA.
J Exp Biol. 2018 Nov 12;221(Pt 22):jeb181834. doi: 10.1242/jeb.181834.
Minimizing the metabolic cost of transport can affect selection of the preferred walking speed. While many factors can affect metabolic cost of transport during human walking, its interaction with step-to-step variability is unclear. Here, we aimed to determine the interaction between metabolic cost of transport and step length variability during human walking at different speeds. In particular, two aspects of step length variability were analyzed: the amount of variations ('variations') and the organization of the step-to-step fluctuations ('fluctuations'). Ten healthy, young participants walked on a treadmill at five speeds, ranging from 0.75 to 1.75 m s Metabolic cost of transport, step length variations (coefficient of variation) and step length fluctuations (quantified via detrended fluctuation analysis) were calculated. A mixed-model ANOVA revealed that variations and walking speed were strong predictors of metabolic cost of transport (=0.917, <0.001), whereas fluctuations were not. Preferred walking speed (1.05±0.20 m s) was not significantly different from the speed at which metabolic cost of transport was minimized (1.04±0.05 m s; =0.792), nor from the speed at which fluctuations were most persistent (1.00±0.41 m s; =0.698). The minimization of variations occurred at a faster speed (1.56±0.17 m s) than the preferred walking speed (<0.001). Step length variations likely affect metabolic cost of transport because greater variations are indicative of suboptimal, mechanically inefficient steps. Fluctuations have little or no effect on metabolic cost of transport, but still may relate to preferred walking speed.
最小化运动代谢成本会影响到人们对最佳步行速度的选择。尽管有许多因素会影响人类步行时的运动代谢成本，但目前尚不清楚其与步长变异性之间的相互作用。在这里，我们旨在确定在不同速度下，运动代谢成本与步长变异性之间的相互作用。具体来说，我们分析了步长变异性的两个方面：变化量（“variations”）和步长波动的组织（“fluctuations”）。10 名健康的年轻参与者在跑步机上以 5 种速度行走，速度范围从 0.75 米/秒到 1.75 米/秒。计算运动代谢成本、步长变异性（变异系数）和步长波动（通过去趋势波动分析进行量化）。混合模型方差分析表明，变化量和步行速度是运动代谢成本的重要预测指标（=0.917，<0.001），而波动量则不是。最佳步行速度（1.05±0.20 米/秒）与运动代谢成本最小化时的速度（1.04±0.05 米/秒；=0.792），以及波动量最持久时的速度（1.00±0.41 米/秒；=0.698）没有显著差异。变化量的最小化速度（1.56±0.17 米/秒）快于最佳步行速度（<0.001）。步长变异性可能会影响运动代谢成本，因为更大的变异性表明步幅不理想，机械效率低下。波动对运动代谢成本的影响较小或没有，但可能与最佳步行速度有关。
