Zai Claire Z, Grabowski Alena M
Department of Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States.
Department of Integrative Physiology, University of Colorado Boulder, 354 UCB, Boulder, CO 80309, United States; Eastern Colorado Healthcare System, Department of Veterans Affairs, Denver, CO, United States.
J Biomech. 2020 Apr 16;103:109667. doi: 10.1016/j.jbiomech.2020.109667. Epub 2020 Jan 27.
The metabolic cost of walking is due to muscle force generated to support body weight (BW), external work performed to redirect and accelerate the center of mass (CoM), and internal work performed to swing the limbs and maintain balance. We hypothesized that BW support would incur a greater and lower percentage of Net Metabolic Power (NMP) for uphill and downhill slopes, respectively, compared to level-ground walking. Additionally, we hypothesized that mass redirection would incur a greater and lower percentage of NMP for uphill and downhill slopes, respectively compared to level-ground walking. 10 subjects walked at 1.25 m/s on 0°, ±3°, and ±6° slopes with reduced/added weight and added mass while we measured metabolic rates. We calculated NMP per Newton of reduced BW at each slope and found that BW support required 58% and 64% of the NMP to walk at +3° and +6°, respectively, both greater than the 15% required for level-ground walking (p < 0.025). We calculated NMP per kg of added mass at each slope and found that mass redirection required 19% and 23% of the NMP to walk at +3° and +6°, respectively, both lower than the 35% required for level-ground walking (p < 0.025). We found no significant differences in the percentage of NMP for BW support or mass redirection during downhill compared to level ground walking (p > 0.05). Our findings elucidate that the percentage of NMP attributed to BW support and mass redirection is different for sloped compared to level-ground walking. These results inform biomimetic assistive device designs aimed at reducing metabolic cost.
行走的代谢成本源于为支撑体重（BW）而产生的肌肉力量、为使质心（CoM）重新定向和加速而进行的外部功，以及为摆动肢体和保持平衡而进行的内部功。我们假设，与平地行走相比，在上坡和下坡时，支撑体重分别会消耗更高和更低比例的净代谢功率（NMP）。此外，我们假设，与平地行走相比，在上坡和下坡时，质量重新定向分别会消耗更高和更低比例的NMP。10名受试者在0°、±3°和±6°的斜坡上以1.25米/秒的速度行走，行走时体重减轻/增加以及增加了质量，同时我们测量了代谢率。我们计算了每个斜坡上每减少一牛顿体重的NMP，发现在上坡3°和6°行走时，支撑体重分别需要58%和64%的NMP，两者均高于平地行走所需的15%（p < 0.025）。我们计算了每个斜坡上每增加一千克质量的NMP，发现在上坡3°和6°行走时，质量重新定向分别需要19%和23%的NMP，两者均低于平地行走所需的35%（p < 0.025）。我们发现下坡时支撑体重或质量重新定向的NMP百分比与平地行走相比没有显著差异（p > 0.05）。我们的研究结果表明，与平地行走相比，斜坡行走时支撑体重和质量重新定向所消耗的NMP百分比有所不同。这些结果为旨在降低代谢成本的仿生辅助设备设计提供了参考。
