Kuo Arthur D
Department of Mechanical Engineering and Biomedical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, MI 48109-2125, USA.
Hum Mov Sci. 2007 Aug;26(4):617-56. doi: 10.1016/j.humov.2007.04.003. Epub 2007 Jul 6.
We examine two prevailing, yet surprisingly contradictory, theories of human walking. The six determinants of gait are kinematic features of gait proposed to minimize the energetic cost of locomotion by reducing the vertical displacement of the body center of mass (COM). The inverted pendulum analogy proposes that it is beneficial for the stance leg to behave like a pendulum, prescribing a more circular arc, rather than a horizontal path, for the COM. Recent literature presents evidence against the six determinants theory, and a simple mathematical analysis shows that a flattened COM trajectory in fact increases muscle work and force requirements. A similar analysis shows that the inverted pendulum fares better, but paradoxically predicts no work or force requirements. The paradox may be resolved through the dynamic walking approach, which refers to periodic gaits produced almost entirely by the dynamics of the limbs alone. Demonstrations include passive dynamic walking machines that descend a gentle slope, and active dynamic walking robots that walk on level ground. Dynamic walking takes advantage of the inverted pendulum mechanism, but requires mechanical work to transition from one pendular stance leg to the next. We show how the step-to-step transition is an unavoidable energetic consequence of the inverted pendulum gait, and gives rise to predictions that are experimentally testable on humans and machines. The dynamic walking approach provides a new perspective, focusing on mechanical work rather than the kinematics or forces of gait. It is helpful for explaining human gait features in a constructive rather than interpretive manner.
我们研究了两种流行但却惊人矛盾的人类行走理论。步态的六个决定因素是步态的运动学特征，其提出通过减少身体质心（COM）的垂直位移来最小化运动的能量消耗。倒立摆类比认为，支撑腿表现得像一个摆锤是有益的，为质心规定了一条更圆的弧线，而不是水平路径。最近的文献提供了反对六个决定因素理论的证据，并且一个简单的数学分析表明，扁平的质心轨迹实际上会增加肌肉做功和力量需求。类似的分析表明，倒立摆的情况更好，但自相矛盾的是，它预测不需要做功或力量。这个矛盾可以通过动态行走方法来解决，动态行走方法指的是几乎完全由肢体动力学产生的周期性步态。示例包括在缓坡上下降的被动动态行走机器，以及在平地上行走的主动动态行走机器人。动态行走利用了倒立摆机制，但需要机械功来从一个支撑腿的摆动状态过渡到下一个。我们展示了步间过渡是倒立摆步态不可避免的能量结果，并产生了可以在人类和机器上进行实验验证的预测。动态行走方法提供了一个新的视角，专注于机械功而不是步态的运动学或力。它有助于以建设性而非解释性的方式解释人类步态特征。
