Difference in Muscle Growth between Concentric, Eccentric, and Isometric Contraction
To determine which type of muscular contraction produces the highest increase in muscle growth is to know how muscles actually grow. The term used for growing muscles is hypertrophy. Hypertrophy is defined as “the growing of an organ or tissue through its cell size” (R.J, Hernandez and L., Kravitz, 2014). In this case, skeletal muscle tissue is what is growing and it is growing through the increase in size of skeletal muscle cells. In order to grow in size, muscle fibers need assistance from a special type of cell called a satellite cell. In adults these cells are typically dormant reserve cells, but when they are activated they differentiate into myoblasts. Satellite cells are activated from a stimulus of muscle damage. This muscle damage usually results from high intensity exercise that puts a load on the muscles that is greater than an average load. “These activated satellite cells then differentiate and fuse together and to damaged skeletal muscle fibers. This fusion of cells results in a larger cross sectional area for the muscle fiber. Some of these cells remain as organelles on the skeletal muscle fibers while the rest differentiate into new muscle protein strands called myofibrils, which are the thicker fibers of the sarcomere. In addition, the satellite cells that differentiate into organelles often differentiate into additional nuclei for the muscle cell, which aids in synthesizing more thin myofilaments called actin. This is aided by the added nuclei synthesizing more proteins than the original amount of nuclei.