MUSCLE PHYSIOLOGY

Detailed explanation-1: -Muscle contraction and relaxation are regulated by the intracellular Ca2+ concentration (1–3). When a muscle fiber is excited, Ca2+ is rapidly released from the sarcoplasmic reticulum (SR) inducing muscle contraction. When Ca2+ is reaccumulated into the SR, the muscle relaxes.

Detailed explanation-2: -An eccentric (lengthening) muscle contraction occurs when a force applied to the muscle exceeds the momentary force produced by the muscle itself, resulting in the forced lengthening of the muscle-tendon system while contracting (Lindstedt et al., 2001).

Detailed explanation-3: -When the muscle relaxes the tension decreases. This phase is called the relaxation phase. During this phase calcium is actively transported back into the sarcoplasmic reticulum using ATP. The troponin moves back into position blocking the myosin binding site on the actin and the muscle passively lengthens.