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Muscle contraction is the activation of tension-generating sites within muscle fibers. In physiology, muscle contraction does not mean muscle shortening because muscle tension can be produced without changes in muscle length such as holding a heavy book or a dumbbell at the same position.he termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state. Muscle contractions can be described based on two variables: length and tension.
eccentric contraction. 1  controlled relaxation of a contracted muscle, movement occurring as a result of the lengthening of the muscle(s). 2  A lengthening action in which a muscle's attachments are drawn away from one another by an external resistance, even though the muscle is activated. Often called negative work.