Reviewing Muscle Cocontraction.

From a purely mechanical standpoint, muscle cocontraction is an inefficient utilization of muscle forces. Muscles resist each other producing little, if any, net movement. In mature gait and posture, as well as in many skilled motor activities, reciprocal activation or inhibition commonly occurs. Muscle cocontraction is frequently seen in infants and toddlers, in persons with central nervous system (CNS) damage, and interestingly, it is also seen in normal adults when they are attempting a novel complex motor skill. How might these three situations be related? This article summarizes the developmental trend of decreasing cocontraction with age. The relationship of cocontraction to motor skill development is described. Finally, the role of co contraction in movement disorders of persons with CNS deficits is explored, and an attempt is made to synthesize the presented material.