Effects of Exercise and Aging on Skeletal Muscle

Abstract

A substantial loss of muscle mass and strength (sarcopenia), a decreased regenerative capacity, and a compromised physical performance are hallmarks of aging skeletal muscle. These changes are typically accompanied by impaired muscle metabolism, including mitochondrial dysfunction and insulin resistance. A challenge in the field of muscle aging is to dissociate the effects of chronological aging per se on muscle characteristics from the secondary influence of lifestyle and disease processes. Remarkably, physical activity and exercise are well-established countermeasures against muscle aging, and have been shown to attenuate age-related decreases in muscle mass, strength, and regenerative capacity, and slow or prevent impairments in muscle metabolism. We posit that exercise and physical activity can influence many of the changes in muscle during aging, and thus should be emphasized as part of a lifestyle essential to healthy aging.

Figure 1.

Sedentary lifestyle contributes to an “unhealthy aging.” (A) In this scenario, impairments on muscle regeneration are exacerbated because of a reduction in satellite cell content and a decreased myogenic potential and increased fibrosis. Unhealthy aging is also characterized by an augmented accumulation of intermuscular adipocytes. Furthermore, obesity is known to exacerbate the low-grade inflammation that occurs with aging. These lifestyle factors may also impair myofiber contractile function. Poor nutrition and physical inactivity are more strongly associated with insulin resistance and mitochondrial dysfunction than chronological age, although they may exacerbate or accelerate loss of muscle mass, strength, and functional performance and energy metabolism. Conversely, exercise can profoundly improve muscle metabolism, strength, and function, which can attenuate or prevent some of the negative age-associated changes and will translate to a “healthy” aging. (B) In this scenario, exercise reduces or delays the declines in muscle regeneration, increases satellite cells and enhances their activation, improves myogenic potential, and reduces fibrosis formation. Exercise can also reduce the age-associated accumulation of intermuscular fat and alter intramyocellular lipids (IMCLs). Exercise improves muscle cell and tissue contractile function. Exercise can robustly improve impaired muscle metabolism, such as insulin resistance and mitochondrial dysfunction, all of which are likely linked to enhanced neuromuscular activation and vascular function. The combination of good nutrition and an active lifestyle can minimize the declines in muscle mass, strength, and physical performance that are observed in older people, all of which likely prevent or delay mobility limitations, disability, institutionalization, and morbidity, translating into healthy aging. This illustration used elements from Servier Medical Art, www.servier.com/Powerpoint-image-bank.