Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
Proc Natl Acad Sci U S A. 2011 Nov 15;108(46):18631-6. doi: 10.1073/pnas.1105277108. Epub 2011 Nov 7.
Humans are known to have energetically optimal walking and running speeds at which the cost to travel a given distance is minimized. We hypothesized that "optimal" walking and running speeds would also exist at the level of individual locomotor muscles. Additionally, because humans are 60-70% more economical when they walk than when they run, we predicted that the different muscles would exhibit a greater degree of tuning to the energetically optimal speed during walking than during running. To test these hypotheses, we used electromyography to measure the activity of 13 muscles of the back and legs over a range of walking and running speeds in human subjects and calculated the cumulative activity required from each muscle to traverse a kilometer. We found that activity of each of these muscles was minimized at specific walking and running speeds but the different muscles were not tuned to a particular speed in either gait. Although humans are clearly highly specialized for terrestrial locomotion compared with other great apes, the results of this study indicate that our locomotor muscles are not tuned to specific walking or running speeds and, therefore, do not maximize the economy of locomotion. This pattern may have evolved in response to selection to broaden the range of sustainable running speeds, to improve performance in motor behaviors not related to endurance locomotion, or in response to selection for both.
人类的行走和奔跑速度存在能量最优值，即在一定距离内消耗的能量最小。我们假设个体运动肌肉也存在“最佳”行走和奔跑速度。此外，由于人类行走比奔跑更节省 60-70%的能量，我们预测不同的肌肉在行走时比在奔跑时会更适应能量最优速度。为了验证这些假设，我们使用肌电图在人类受试者的行走和奔跑速度范围内测量了背部和腿部的 13 块肌肉的活动，并计算了每个肌肉完成一公里所需的累积活动量。我们发现，这些肌肉中的每一块肌肉在特定的行走和奔跑速度下的活动量最小，但不同的肌肉在任何一种步态中都没有针对特定的速度进行调整。虽然与其他大型猿类相比，人类在陆地运动方面显然具有高度的专门化，但这项研究的结果表明，我们的运动肌肉并没有针对特定的行走或奔跑速度进行调整，因此无法最大限度地提高运动的经济性。这种模式可能是为了适应更广泛的可持续奔跑速度的选择、提高与耐力运动无关的运动行为的表现、或者适应两者的选择而进化的。
