Development of Bipedal and Quadrupedal Locomotion in Humans from a Dynamical Systems Perspective

Locomotion is the movement of an organism from one place to another, often by the action of appendages such as flagella, limbs, or wings. In some animals, such as fish, locomotion results from a wavelike series of muscle contractions (The American Heritage® Science Dictionary, 2005). Walking is the act of traveling by foot; gait is the manner of walking; running is the act of traveling on foot at a fast pace; crawling is a slow mode of hand-knee or hand-foot locomotion. Quadrupedal locomotion, walking on all four extremities, is the most remarkable trait of the quadruped animals, and has been elegantly elaborated by dynamic selection processes over millions of years. Non-primate mammals usually utilize lateralsequence quadrupedalism, in which the hindlimb footfall leads the ipsilateral forelimb, whereas the non-human primates utilize a diagonal-sequence quadrupedalism, in which the hindlimb moves with the contralateral forelimb in a diagonal couplet. The neural control for the quadrupedal and bipedal locomotor processes in monkeys may also be applicable to human locomotion (Xiang, 2007).