Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, The Netherlands.
Gait Posture. 2011 Apr;33(4):544-9. doi: 10.1016/j.gaitpost.2011.01.007. Epub 2011 Feb 16.
The energy cost of walking could be attributed to energy related to the walking movement and energy related to balance control. In order to differentiate between both components we investigated the energy cost of walking an enforced step pattern, thereby perturbing balance while the walking movement is preserved. Nine healthy subjects walked three times at comfortable walking speed on an instrumented treadmill. The first trial consisted of unconstrained walking. In the next two trials, subject walked while following a step pattern projected on the treadmill. The steps projected were either composed of the averaged step characteristics (periodic trial), or were an exact copy including the variability of the steps taken while walking unconstrained (variable trial). Metabolic energy cost was assessed and center of pressure profiles were analyzed to determine task performance, and to gain insight into the balance control strategies applied. Results showed that the metabolic energy cost was significantly higher in both the periodic and variable trial (8% and 13%, respectively) compared to unconstrained walking. The variation in center of pressure trajectories during single limb support was higher when a gait pattern was enforced, indicating a more active ankle strategy. The increased metabolic energy cost could originate from increased preparatory muscle activation to ensure proper foot placement and a more active ankle strategy to control for lateral balance. These results entail that metabolic energy cost of walking can be influenced significantly by control strategies that do not necessary alter global gait characteristics.
行走的能量消耗可归因于与行走运动相关的能量和与平衡控制相关的能量。为了区分这两个组成部分，我们研究了在强制步幅模式下行走的能量消耗，从而在保持行走运动的同时干扰平衡。九名健康受试者以舒适的行走速度在装有仪器的跑步机上行走三次。第一次试验包括不受限制的行走。在接下来的两次试验中，受试者在跟随跑步机上投影的步幅模式行走。投影的步幅要么由平均步幅特征组成（周期性试验），要么是包括在不受限制行走时所采取的步幅变化的精确副本（变量试验）。评估代谢能量成本，并分析压力中心轮廓以确定任务表现，并深入了解所应用的平衡控制策略。结果表明，与不受限制的行走相比，周期性试验和变量试验的代谢能量成本都显著更高（分别为 8%和 13%）。在单腿支撑期间，当强制步态模式时，压力中心轨迹的变化更大，这表明踝关节策略更活跃。代谢能量成本的增加可能源于增加预备性肌肉激活以确保正确的足部放置和更活跃的踝关节策略以控制侧向平衡。这些结果表明，行走的代谢能量成本可能会受到不需要改变整体步态特征的控制策略的显著影响。
