Gait changes in a line of mice artificially selected for longer limbs.
Gait changes in a line of mice artificially selected for longer limbs.
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作者：
Sparrow LM;Pellatt E;Yu SS;Raichlen DA;Pontzer H;Rolian C
在腿式陆地运动中，站立阶段（即肢体与基质接触时）的持续时间与肢体长度呈正相关，与运输的代谢成本呈负相关。这些关系在种间水平上、在各种体型和行驶速度范围内都有详细记录。然而，这种关系在物种内部（即自然选择发挥作用的地方）更难评估，这主要是出于实际原因，包括肢体长度的群体差异较小，以及体重或训练等混杂因素的存在。在这里，我们比较了 Longshanks（一种通过人工选择产生的长腿小鼠品系）和在相同条件下饲养的随机繁殖、质量匹配的对照小鼠的步态时空运动学。我们使用步态跑步机来测试以下假设：与对照组相比，长腿犬具有更长的站立阶段和步幅长度，并且前肢和后肢的步幅频率降低。我们的结果表明两组之间的步态存在显着差异。具体来说，正如假设的那样，长腿组的站立持续时间和步幅比对照组长 8-10%，而步幅频率比对照组低 8%。然而，两条线之间的爪子触地时间和顺序没有差异。总而言之，这些数据表明，对于给定的速度，与对照组相比，长腿小鼠在完成相同的距离或跑步时间时需要显着更少、更长的步数，这对于衡量个体整体性能差异的其他指标（例如运输的代谢成本）具有重要意义。
In legged terrestrial locomotion, the duration of stance phase, i.e., when limbs are in contact with the substrate, is positively correlated with limb length, and negatively correlated with the metabolic cost of transport. These relationships are well documented at the interspecific level, across a broad range of body sizes and travel speeds. However, such relationships are harder to evaluate within species (i.e., where natural selection operates), largely for practical reasons, including low population variance in limb length, and the presence of confounding factors such as body mass, or training. Here, we compared spatiotemporal kinematics of gait in Longshanks, a long-legged mouse line created through artificial selection, and in random-bred, mass-matched Control mice raised under identical conditions. We used a gait treadmill to test the hypothesis that Longshanks have longer stance phases and stride lengths, and decreased stride frequencies in both fore- and hind limbs, compared with Controls. Our results indicate that gait differs significantly between the two groups. Specifically, and as hypothesized, stance duration and stride length are 8–10% greater in Longshanks, while stride frequency is 8% lower than in Controls. However, there was no difference in the touch-down timing and sequence of the paws between the two lines. Taken together, these data suggest that, for a given speed, Longshanks mice take significantly fewer, longer steps to cover the same distance or running time compared to Controls, with important implications for other measures of variation among individuals in whole-organism performance, such as the metabolic cost of transport.