Diedrich F J, Warren W H
Department of Cognitive and Linguistic Sciences, Brown University, Providence, Rhode Island 02912.
J Exp Psychol Hum Percept Perform. 1995 Feb;21(1):183-202. doi: 10.1037//0096-1523.21.1.183.
Why do humans switch from walking to running at a particular speed? It is proposed that gait transitions behave like nonequilibrium phase transitions between attractors. Experiment 1 examined walking and running on a treadmill while speed was varied. The transition occurred at the equal-energy separatrix between gaits, with predicted shifts in stride length and frequency, a qualitative reorganization in the relative phasing of segments within a leg, a sudden jump in relative phase, enhanced fluctuations in relative phase, and hysteresis. Experiment 2 dissociated speed, frequency, and stride length to show that the transition occurred at a constant speed near the energy separatrix. Results are consistent with a dynamic theory of locomotion in which preferred gaits are characterized by stable phase relationships and minimum energy expenditure, and gait transitions by a loss of stability and the reduction of energetic costs.
为什么人类会在特定速度下从行走切换到跑步？有人提出，步态转变的行为类似于吸引子之间的非平衡相变。实验1在跑步机上改变速度的同时观察行走和跑步。转变发生在步态之间的等能量分离线上，伴随着步幅和频率的预测变化、腿部各节段相对相位的定性重组、相对相位的突然跳跃、相对相位波动的增强以及滞后现象。实验2分离了速度、频率和步幅，以表明转变发生在能量分离线附近的恒定速度处。结果与运动的动态理论一致，即优选步态的特征是稳定的相位关系和最小的能量消耗，而步态转变则是稳定性丧失和能量成本降低的结果。
