ACTIVITY OF MOTOR UNITS DURING CONCENTRIC AND ECCENTRIC CONTRACTIONS

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Abstract
The biomechanics of the foot and ankle are initially discussed, as a series of isolated joints and segments, and subsequently as an integrated unit during the functional activities of walking and running. The kinematics and kinetics of the foot and ankle during the three major components of stance phase are reviewed. The first component, between foot contact and foot flat, is characterized primarily by force absorption. The portion of the gait cycle between foot flat and heel off is associated with controlled forward progression of the center of mass and maximum mobility of the transverse tarsal joint. In the third phase, supination of the foot results in increased rigidity of the transverse tarsal joint, and therefore improved force transmission. The controversy regarding the function of the triceps surae during this phase of the gait cycle is discussed.