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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 contractions: A concentric contraction is a type of muscle contraction where the length of the muscles shorten while undergoing tension. For example, when you pick up a curl bar and perform a biceps curl, the length of your biceps muscles shorten.Your hands start down by your sides, and ends with your hands up by your shoulders.his is another example of a voluntary eccentric contraction. b) Involuntary eccentric contractions: Involuntary eccentric contractions occur when the weight or resistance you are attempting to move or lift is too heavy or strong for the muscle to accommodate.