Myers M J, Steudel K, White S C
Department of Zoology, University of Wisconsin-Madison 53706.
J Exp Zool. 1993 Mar 1;265(3):211-23. doi: 10.1002/jez.1402650303.
Although the metabolic cost of running has been found to vary systematically with running speed and body mass in animals, no mechanistic model of cost determination has been widely accepted. Because two suggested cost determinants--mechanical power output and the rate of force application--covary with running speed when gait (stride frequency) is unconstrained, examining the influence of each factor on cost has been problematic. We experimentally uncoupled the usual relationships between three readily manipulated cost correlates--speed, stride frequency, and mass distribution--to study the determinants of the cost of running in humans along a section of the cost response surface. Two levels of each cost correlate were used in a factorial design in which subjects ran at all eight combinations of factor levels while rate of oxygen consumption (VO2), mechanical power, and contact time were measured as response variables. Contact time and mechanical power were measured from high-speed cinefilm. Mechanical power accounted for 88%, and contact time (rate of force application) 57%, of speed-related VO2 variation. Variation in cost produced by changes in stride frequency and mass distribution were largely explained by mechanical power. Contact time was not significantly correlated with overall variation in VO2, while mechanical power output explained 80% of that variation. For the range of conditions tested, we conclude that the mechanical power derived from muscular contractions is an important determinant of the cost of running. While we have shown that the rate at which muscles shorten is not the sole determinant of the cost of running, the extent to which this factor influences cost remains unclear.
尽管已发现动物奔跑的代谢成本会随着奔跑速度和体重而系统性变化，但尚未有一个关于成本确定的机理模型被广泛接受。由于两个被认为的成本决定因素——机械功率输出和力的施加速率——在步态（步频）不受限时会与奔跑速度共同变化，因此研究每个因素对成本的影响一直存在问题。我们通过实验解开了三个易于操控的成本相关因素——速度、步频和质量分布——之间的通常关系，以沿着成本响应面的一部分研究人类奔跑成本的决定因素。在析因设计中使用了每个成本相关因素的两个水平，让受试者以所有八种因素水平组合进行奔跑，同时测量耗氧率（VO2）、机械功率和接触时间作为响应变量。接触时间和机械功率通过高速电影胶片测量。机械功率占与速度相关的VO2变化的88%，接触时间（力的施加速率）占57%。步频和质量分布变化所产生的成本变化在很大程度上由机械功率解释。接触时间与VO2的总体变化没有显著相关性，而机械功率输出解释了该变化的80%。对于所测试的条件范围，我们得出结论，肌肉收缩产生的机械功率是奔跑成本的一个重要决定因素。虽然我们已经表明肌肉缩短的速率不是奔跑成本的唯一决定因素，但该因素对成本的影响程度仍不清楚。
