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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.
(concentric action) the 'true' form of contraction of a muscle in which it shortens against a load (which may be only that of gravity on the relevant body part), and so does positive work. Hence concentric exercise: that in which the principal agonists act concentrically.See also muscle contraction.alled also shortening contraction. Dupuytren's contraction Dupuytren's contracture. eccentric contraction contraction in the presence of a resistive force that results in elongation of a muscle, used to perform negative work or to decelerate a body part.