Timing of head movements is consistent with energy minimization in walking ungulates
Timing of head movements is consistent with energy minimization in walking ungulates
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DOI：
10.1098/rspb.2016.1908
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发表时间：
2016-11-30
影响因子：
4.7
通讯作者：
Nyakatura, John A.
中科院分区：
文献类型：
--
作者：
Loscher, David M.;Meyer, Fiete;Nyakatura, John A.
许多有蹄类动物在行走时会表现出明显的点头动作。到目前为止，这种行为的功能意义仍不清楚。将四足哺乳动物的体内运动学与计算机模型相结合，我们表明头部和颈部垂直位移的时间与以倒立摆行走步态携带这些身体部位的能量消耗最小化是一致的。改变模型中头部运动的时间会导致携带头部和颈部的代谢成本估计增加高达 63%。头颈单元的振动导致重力振动传递到前肢。有利的时机增加了单个支撑阶段的负载，其中重定向质心（COM）的轨迹被认为是能量廉价的。在双支撑期间，根据碰撞力学，COM脉冲的方向变化是昂贵的，观察到的时间减少了负载。由于头部和颈部约占体重的 10%，因此此处显示的效果也会影响动物的总体能量消耗。这种机制类似于高科技背包中用于节能负载运输的机制，在有蹄类动物中广泛存在，并为动物如何节省运动提供了见解。
Many ungulates show a conspicuous nodding motion of the head when walking. Until now, the functional significance of this behaviour remained unclear. Combining in vivo kinematics of quadrupedal mammals with a computer model, we show that the timing of vertical displacements of the head and neck is consistent with minimizing energy expenditure for carrying these body parts in an inverted pendulum walking gait. Varying the timing of head movements in the model resulted in increased metabolic cost estimate for carrying the head and neck of up to 63%. Oscillations of the head-neck unit result in weight force oscillations transmitted to the forelimbs. Advantageous timing increases the load in single support phases, in which redirecting the trajectory of the centre of mass (COM) is thought to be energetically inexpensive. During double support, in which-according to collision mechanics-directional changes of the impulse of the COM are expensive, the observed timing decreases the load. Because the head and neck comprise approximately 10% of body mass, the effect shown here should also affect the animals' overall energy expenditure. This mechanism, working analogously in high-tech backpacks for energy-saving load carriage, is widespread in ungulates, and provides insight into how animals economize locomotion.