Browning Raymond C, Baker Emily A, Herron Jessica A, Kram Rodger
Dept. of Integrative Physiology, 354 UCB, Univ. of Colorado, Boulder, CO 80309-0354, USA.
J Appl Physiol (1985). 2006 Feb;100(2):390-8. doi: 10.1152/japplphysiol.00767.2005. Epub 2005 Oct 6.
The metabolic energy cost of walking is determined, to a large degree, by body mass, but it is not clear how body composition and mass distribution influence this cost. We tested the hypothesis that walking would be most expensive for obese women compared with obese men and normal-weight women and men. Furthermore, we hypothesized that for all groups, preferred walking speed would correspond to the speed that minimized the gross energy cost per distance. We measured body composition, maximal oxygen consumption, and preferred walking speed of 39 (19 class II obese, 20 normal weight) women and men. We also measured oxygen consumption and carbon dioxide production while the subjects walked on a level treadmill at six speeds (0.50-1.75 m/s). Both obesity and sex affected the net metabolic rate (W/kg) of walking. Net metabolic rates of obese subjects were only approximately 10% greater (per kg) than for normal-weight subjects, and net metabolic rates for women were approximately 10% greater than for men. The increase in net metabolic rate at faster walking speeds was greatest in obese women compared with the other groups. Preferred walking speed was not different across groups (1.42 m/s) and was near the speed that minimized gross energy cost per distance. Surprisingly, mass distribution (thigh mass/body mass) was not related to net metabolic rate, but body composition (% fat) was (r2= 0.43). Detailed biomechanical studies of walking are needed to investigate whether obese individuals adopt novel energy saving mechanisms during walking.
步行的代谢能量消耗在很大程度上由体重决定，但身体成分和质量分布如何影响这种消耗尚不清楚。我们检验了这样一个假设：与肥胖男性以及正常体重的女性和男性相比，肥胖女性步行的成本最高。此外，我们还假设，对于所有组而言，偏好的步行速度将与使每距离总能量消耗最小化的速度相对应。我们测量了39名（19名II级肥胖者、20名正常体重者）女性和男性的身体成分、最大耗氧量以及偏好的步行速度。我们还测量了受试者在水平跑步机上以六种速度（0.50 - 1.75米/秒）行走时的耗氧量和二氧化碳产生量。肥胖和性别都会影响步行的净代谢率（瓦/千克）。肥胖受试者的净代谢率仅比正常体重受试者高约10%（每千克），女性的净代谢率比男性高约10%。与其他组相比，肥胖女性在较快步行速度下净代谢率的增加最大。各组的偏好步行速度没有差异（1.42米/秒），且接近使每距离总能量消耗最小化的速度。令人惊讶的是，质量分布（大腿质量/身体质量）与净代谢率无关，但身体成分（脂肪百分比）却与之相关（r² = 0.43）。需要对步行进行详细的生物力学研究，以调查肥胖个体在步行过程中是否采用了新的节能机制。
