Cardiovascular, neuromuscular, and metabolic alterations with age leading to frailty.

As members of our society live longer, a greater percentage of the population will be older. These demographic changes will stress our social and medical delivery system, unless interventions can alter the course leading to frailty. Maximal aerobic power decreases with age, due to a decrease in cardiac output, and is exacerbated by cardiovascular disease. Asymptomatic aging does not reduce cardiovascular function to an extent that would lead to loss of function. Metabolism, endurance, and contraction velocity and muscle strength remain relatively high until 40, 50, and 60 years of age, respectively. After age 60, there are dramatic decreases (approximately 10% per year) which lead to loss of function and independence. The loss of muscle function leads to an increase in the likelihood of falls (approximately 4-fold). Exercise programs utilizing "aerobic" exercise activities do not lead to an increase in muscle function, whereas programs designed specifically for muscle can increase function and, presumably, reduce the risk of falls and injuries.