Muscle mass decreases as people age because the size and number of muscle fibers decrease with age. A lifestyle that is too relaxed or sedentary can increase the loss of muscle mass, and can even lead to atrophy in older patients, according to the American Academy of Orthopedic Surgeons.
Even the heart muscle becomes weaker as people age. The heart can struggle to pump large quantities of blood to the rest of the body. Tendons, which attach muscle to bone, also lose water and become more brittle with age. Because the tendons are less tolerable to stress, muscles can become weaker more quickly. One of the best ways to keep muscles strong through aging is to have an active and healthy lifestyle.