Pain and Fatigue after Concentric and Eccentric Muscle Contractions

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Abstract
Normal subjects performed a step test in which the quadriceps of 1 leg contracted concentrically while the contralateral muscle contracted eccentrically. Maximum voluntary force and the force:frequency relationship were altered bilaterally as a result of the exercise, the changes being greater in the muscle which had contracted eccentrically. Recovery occurred over 24 h. Electromyographic studies using 3 sites on each muscle showed an increase in electrical activation during the exercise only in the muscle which was contracting eccentrically. Recovery followed a time course similar to that of the contractile properties. Pain and tenderness developed only in the muscle which had contracted eccentrically. Pain was first noted .apprx. 8 h after exercise and was maximal at .apprx. 48 h after exercise, at which time force generation and electrical activation had returned to preexercise values. Eccentric contractions cause more profound changes in some aspects of muscle function than concentric contractions. These changes cannot be explained in simple metabolic terms. They may be the result of mechanical trauma caused by the high tension generated in relatively few active fibers during eccentric contractions.