Study of eccentric-concentric contraction of the upper extremity muscles.

Abstract The stretching of a muscle prior to subsequent concentric contraction enhances utilization of the muscle properties and has a positive influence on the velocity at a certain contraction level. The aim of this paper is to define the optimum load necessary for the muscle to stretch for a given subject to obtain the best result in concentric contraction of the upper extremity muscles. Eighteen college-age male subjects participated in the experiment. Kinematic measurements of the extremity by means of a special pendulum were carried out. The test consisted of attempts by subjects to push the pendulum as far as possible (1) from the stationary position and (2) after the swinging pendulum which caused the eccentric contraction of the muscles to take place had come to rest. It was found that an increase of the eccentric load represented by the velocity of the mass of the swinging pendulum helps the pushing performance but the improvements obtained are inversely proportional to the load. Secondly, the mean ratio of the velocity of the eccentric contraction to that of concentric contraction increases from 0.48 to 1.37 with the load used.