compare concentric and eccentric contractions. concentric contractions occur when the muscle tension exceeds the load, and the muscle shortens. eccentric contractions occur when the muscle tension is less than the load, and the muscle elongates. concentric contractions consist of equal lengths of time contracting and relaxing. eccentric contractions consist of a longer time relaxing than contracting. concentric contractions occur when the tension produced never exceeds the load, and the muscle does not change length. eccentric contractions occur when the tension produced exceeds the load, and the muscle shortens. concentric contractions occur when the muscle tension is less than the load, and the muscle elongates. eccentric contractions occur when the muscle tension exceeds the load, and the muscle shortens. concentric contractions consist of equal lengths of time contracting and relaxing. eccentric contractions consist of a longer time contracting than relaxing.