The major issues in this review paper include the theories of aging, and the structure and physiological changes of nervous system, musculoskeletal system and cardiovascular system in the elderly. The theories of aging include genetic and nongenetic control. The major deteorations of the nervous system in the elderly is in the central nervous system, not peripheral. The common symptoms include the impaiment of memory, learning, balance and movement etc. The major causes of musele weakness and bone fracture in the elderly is the changes of musculoskeletal system, such as muscle atrophy, fibrosis and osteoporosis. In terms of exercise capacity, the deterioration of the cardiopulmonary functions becomes the major limiting factor to exercise in the old person. Therefore, those in- formations provide the guideline for exercise training in geriatrics.