Children and adults minimise activated muscle volume by selecting gait parameters that balance gross mechanical power and work demands.
Children and adults minimise activated muscle volume by selecting gait parameters that balance gross mechanical power and work demands.
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DOI：
10.1242/jeb.122135
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发表时间：
2015-09
期刊：
影响因子：
--
通讯作者：
Usherwood JR
中科院分区：
文献类型：
--
作者：
Hubel TY;Usherwood JR
腿在陆地上的运动消耗能量。与骑自行车或游泳或飞行动物的运动相比，步行和跑步是非常不经济的。以前已经确定了可以最大限度地减少机械功的双腿步态，并且大致适合以适当的速度行走和跑步。此外，“肌肉力量成本”方法可以有效地将运动动力学与代谢成本联系起来。然而，很少有人解释为什么动物会偏离工作最小化或肌肉力量最小化策略。此外，目前还没有关于运动动力学随动物体型和速度变化的机制解释。在这里，我们报告了步行儿童和成年人的地面反作用力的测量结果，以及他们在跑步过程中的站立持续时间。我们发现，步态动力学和运动学的许多方面随着速度和体型的变化而变化，其方式与最大限度地减少机械功和功率之间要求更高的肌肉激活需求是一致的：分散肌肉动作的持续时间可以减少对功率的激活需求，但代价是更大的工作需求。对于较大的两足动物（成年人）来说，机械工作的要求相对更高，因为与较小的两足动物（儿童）相比，他们在行走时具有对称的 M 形垂直力轨迹，并且在跑步时的站立持续时间相对较短。小孩子的步态，以及他们的力学与最小化工作策略的更大偏差，可以被理解为适合他们的规模，而不仅仅是成人步态的不成熟、不完全发展和能量次优版本。重点文章：儿童和成人行走和跑步的总体力学支持一种新的地面运动成本模型——肌肉激活以产生机械功或动力。
Terrestrial locomotion on legs is energetically expensive. Compared with cycling, or with locomotion in swimming or flying animals, walking and running are highly uneconomical. Legged gaits that minimise mechanical work have previously been identified and broadly match walking and running at appropriate speeds. Furthermore, the ‘cost of muscle force’ approaches are effective in relating locomotion kinetics to metabolic cost. However, few accounts have been made for why animals deviate from either work-minimising or muscle-force-minimising strategies. Also, there is no current mechanistic account for the scaling of locomotion kinetics with animal size and speed. Here, we report measurements of ground reaction forces in walking children and adult humans, and their stance durations during running. We find that many aspects of gait kinetics and kinematics scale with speed and size in a manner that is consistent with minimising muscle activation required for the more demanding between mechanical work and power: spreading the duration of muscle action reduces activation requirements for power, at the cost of greater work demands. Mechanical work is relatively more demanding for larger bipeds – adult humans – accounting for their symmetrical M-shaped vertical force traces in walking, and relatively brief stance durations in running compared with smaller bipeds – children. The gaits of small children, and the greater deviation of their mechanics from work-minimising strategies, may be understood as appropriate for their scale, not merely as immature, incompletely developed and energetically sub-optimal versions of adult gaits. Highlighted Article: The gross mechanics of walking and running children and adults support a new model for the costs dominating level terrestrial locomotion – muscle activation for mechanical work or power.