AN EXPERIMENTAL ANALYSIS OF HUMAN LOCOMOTION

Publisher Website
Google Scholar
Abstract
In limb oscillation, walking and running the movement cycles of the thigh and leg show long, ballistic strokes, one forward and one backward. Between these ballistic strokes the movement of the limb is decelerated, reversed and accelerated by a muscular contraction (a period of more-than-normal tension as shown by action currents and deformation). During the contraction of the agonist the antagonist is relaxed, and during the ballistic phase of the stroke both muscles are relaxed. The contraction of the agonist begins during the backstroke while the limb is lengthening the muscle (pliometric conditions). It continues under substantially isometric condi- tions and then, in the early part of the beatstroke, under shortening (miometric) conditions. Tension development (action current and hardening of the muscle) occurs under pliometric and substantially isometric conditions. Deformation continues under miometric conditions during the acceleration of the limb as the tension is transformed into kinetic energy. Posture and movement depend on the same musculature and upon muscular tension developed under similar conditions. Postural contractions counteract forces that tend to lengthen certain muscles during the movement cycle. Tension, is therefore, developed under pliometric and essentially isometric conditions. Posture is the support from which the agonist drives the movement. This support is not rigid; it may be the momentum of a segment of the body, or it may be a concomitant stroke or series of strokes developing momentarily and disappearing as the agonist relaxes. The rate at which free ballistic movements can be repeated is limited. At a certain rate co-contractions are inevitable and the movement cycle breaks down into a fixation. This rate in limb oscillation is between 2 and 2.5 cycles p. s. The relatively high efficiency of human locomotion depends on the use of long, ballistic strokes, upon the avoidance of co-contractions and fixations, and upon the development of tension for both driving and postural contractions under pliometric and substantially isometric conditions.

This publication has 3 references indexed in Scilit: