running, walking, dancing. high blood vessels, high mitochondria, high myogloin. keep tissue aerobic
weight lifting, resistance. hypertrophy (enlargens) size of diameter increases more myofibrils. more glycogen. more sarcomeres and crossbridges. satellite cells fuse and divide making muscle cell bigger. no mitosis in mature muscle cell
effects of disuse
atrophy. chronic inactivity causes the muscle cells to get smaller. low myofibrils, less sarcomeres. weakens
male sex hormone. stimulates growth of skeletal muscle. high lean muscle mass.