Inactivity accelerates muscle catabolism, mitochondrial dysfunction, and oxidative stress accumulation and reduces aerobic capacity . These problems can lead to a "vicious circle" of muscle loss, injury, and inefficient repair, causing elderly people to become increasingly sedentary over time. Thus, it is imperative to implement preventive and therapeutic strategies to boost muscle mass and regeneration in the elderly and hence maintain and improve both their health and independence and prevent the occurrence of the frailty condition.
Current evidence certainly indicates that a regular exercise program reduces and/or prevents a number of functional declines associated with aging. Since, besides genetic, environmental, and nutritional factors, the lack of physical activity plays a major role in the pathophysiology of frailty, regular exercise has also the potential to reduce the incidence of this problematic expression of population aging. Older adults can adapt and respond to both endurance and strength training. Aerobic/endurance exercise helps to maintain and improve cardiovascular and respiratory function, whereas strength/resistance-exercise programs have been found to be helpful in improving muscle strength, power development, and function.
In this review we describe the pleiotropic effect of physical activity on multiple targets that have a role in preventing the decline of mitochondrial "quality," which is implicated in the aging process of skeletal muscle. Recent evidences consistently show that the "quality" of skeletal muscle mitochondria declines during aging. Indeed, in this condition we can observe (i) mitochondrial DNA mutations; (ii) specific epigenetic drift; (iii) decreased expression of mitochondrial proteins; (iv) reduced enzyme activity of cellular respiration; (v) reduced total mitochondrial content; (vi) increased morphological changes; (vii) a decrease in mitochondrial turnover. All of these factors probably contribute to age-associated sarcopenia, and a growing body of evidence suggests that most of these skeletal muscle age-related changes can be prevented and or attenuated by physical activity. In short, physical activity should be prescribed for older adults. It not only improves physical function, helping the elderly to maintain independence, but also enhances overall health and increases longevity.