Pontzer Herman, Holloway John H, Raichlen David A, Lieberman Daniel E
Department of Anthropology, Washington University, 119 McMillan Hall, Saint Louis, MO 63130, USA.
J Exp Biol. 2009 Feb;212(Pt 4):523-34. doi: 10.1242/jeb.024927.
We investigated the control and function of arm swing in human walking and running to test the hypothesis that the arms act as passive mass dampers powered by movement of the lower body, rather than being actively driven by the shoulder muscles. We measured locomotor cost, deltoid muscle activity and kinematics in 10 healthy adult subjects while walking and running on a treadmill in three experimental conditions: control; no arms (arms folded across the chest); and arm weights (weights worn at the elbow). Decreasing and increasing the moment of inertia of the upper body in no arms and arm weights conditions, respectively, had corresponding effects on head yaw and on the phase differences between shoulder and pelvis rotation, consistent with the view of arms as mass dampers. Angular acceleration of the shoulders and arm increased with torsion of the trunk and shoulder, respectively, but angular acceleration of the shoulders was not inversely related to angular acceleration of the pelvis or arm. Restricting arm swing in no arms trials had no effect on locomotor cost. Anterior and posterior portions of the deltoid contracted simultaneously rather than firing alternately to drive the arm. These results support a passive arm swing hypothesis for upper body movement during human walking and running, in which the trunk and shoulders act primarily as elastic linkages between the pelvis, shoulder girdle and arms, the arms act as passive mass dampers which reduce torso and head rotation, and upper body movement is primarily powered by lower body movement.
我们研究了人类行走和跑步时手臂摆动的控制与功能，以验证以下假设：手臂作为由下半身运动驱动的被动质量阻尼器，而非由肩部肌肉主动驱动。我们在三种实验条件下，对10名健康成年受试者在跑步机上行走和跑步时的运动成本、三角肌活动和运动学进行了测量：对照组；无手臂（双臂交叉于胸前）；以及手臂负重（肘部佩戴重物）。在无手臂和手臂负重条件下，分别减小和增加上半身的转动惯量，对头偏航以及肩部与骨盆旋转之间的相位差产生了相应影响，这与将手臂视为质量阻尼器的观点一致。肩部和手臂的角加速度分别随躯干和肩部的扭转而增加，但肩部的角加速度与骨盆或手臂的角加速度并非呈负相关。在无手臂试验中限制手臂摆动对运动成本没有影响。三角肌的前部和后部同时收缩，而非交替发力来驱动手臂。这些结果支持了人类行走和跑步过程中上半身运动的被动手臂摆动假说，即躯干和肩部主要作为骨盆、肩胛带和手臂之间的弹性连接，手臂作为被动质量阻尼器减少躯干和头部的旋转，并且上半身运动主要由下半身运动驱动。
