Speed, stride frequency and energy cost per stride: how do they change with body size and gait?
Speed, stride frequency and energy cost per stride: how do they change with body size and gait?
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发表时间：
1988-09
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通讯作者：
N. Heglund;C. Taylor
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作者：
N. Heglund;C. Taylor
在这项研究中，我们调查如何速度和步频随身体大小的变化。我们使用这些信息来定义不同大小的动物的“等效速度”，并探讨在这些速度下小鼠和马大小的动物之间运动的质量特定能量成本的六倍差异的潜在因素。在跑步机上测量了16种野生和家养四足动物的速度和步频，从30 g小鼠到200 kg马。我们发现，小跑和疾驰中的最小、首选和最大持续速度都以相同的方式随着身体大小而发生变化，小鼠和马之间的差异为9倍（即所有三种速度都与体重的0.2次方有关）。虽然绝对速度差异很大，但最大可持续速度约为小跑中最小可持续速度的2.6倍，而在疾驰中则为2.1倍。用于维持等效速度（除了最小小跑速度）的频率与体重的-0.15次方因子大致相同。结合这一速度和频率的数据与先前公布的数据上的运动的能量成本，我们发现，运动的质量特定的能量成本几乎是成正比的步幅频率，用于维持恒定的速度在所有的等效速度内小跑和疾驰，除了最小的小跑速度（在那里它的变化的两个因素的大小范围内的动物研究）。因此，在六种等效速度中的五种速度下，每公斤每步的能量成本对于所有动物来说大致相同，与身体大小无关，但随着速度的增加而增加：在首选小跑速度下为5.0 J kg-1 stride-1; 5.3 J kg-1 stride-1在小跑-疾驰过渡速度下;在首选疾驰速度下为7.5 J kg-1 stride-1;在最大持续跑速时，平均每步9.4J kg ~（-1）。运动的成本主要取决于激活肌肉的成本和在单位时间内产生单位力的成本。我们的数据表明，这两种成本都直接随着不同大小的动物以相同速度使用的步频而增加。在快步和疾驰中，随着步幅长度的增加，每一步的肌肉成本增加（对于相同的地面反作用力，需要更高的肌肉力量）。
In this study we investigate how speed and stride frequency change with body size. We use this information to define 'equivalent speeds' for animals of different size and to explore the factors underlying the six-fold difference in mass-specific energy cost of locomotion between mouse- and horse-sized animals at these speeds. Speeds and stride frequencies within a trot and a gallop were measured on a treadmill in 16 species of wild and domestic quadrupeds, ranging in body size from 30 g mice to 200 kg horses. We found that the minimum, preferred and maximum sustained speeds within a trot and a gallop all change in the same rather dramatic manner with body size, differing by nine-fold between mice and horses (i.e. all three speeds scale with about the 0.2 power of body mass). Although the absolute speeds differ greatly, the maximum sustainable speed was about 2.6-fold greater than the minimum within a trot, and 2.1-fold greater within a gallop. The frequencies used to sustain the equivalent speeds (with the exception of the minimum trotting speed) scale with about the same factor, the -0.15 power of body mass. Combining this speed and frequency data with previously published data on the energetic cost of locomotion, we find that the mass-specific energetic cost of locomotion is almost directly proportional to the stride frequency used to sustain a constant speed at all the equivalent speeds within a trot and a gallop, except for the minimum trotting speed (where it changes by a factor of two over the size range of animals studied). Thus the energy cost per kilogram per stride at five of the six equivalent speeds is about the same for all animals, independent of body size, but increases with speed: 5.0 J kg-1 stride-1 at the preferred trotting speed; 5.3 J kg-1 stride-1 at the trot-gallop transition speed; 7.5 J kg-1 stride-1 at the preferred galloping speed; and 9.4 J kg-1 stride-1 at the maximum sustained galloping speed. The cost of locomotion is determined primarily by the cost of activating muscles and of generating a unit of force for a unit of time. Our data show that both these costs increase directly with the stride frequency used at equivalent speeds by different-sized animals. The increase in cost per stride with muscles (necessitating higher muscle forces for the same ground reaction force) as stride length increases both in the trot and in the gallop.