Sarcopenie en het effect van bewegen op spieren en het immuunsysteem.

There is growing evidence for the involvement of inflammatory processes in the development and progression of several age-related conditions, among which sarcopenia (age-related loss of muscle mass) and frailty (one of the major geriatric syndromes) (Bautmans et al., 2009). In fact, ageing, even in healthy persons, is commonly accompanied by slightly elevated concentrations of circulating pro-inflammatory mediators (such as Interleukin[IL]-6 and Tumor Necrosis Factor-alpha), a phenomenon corresponding to a chronic low-grade inflammatory profile (CLIP) (Beyer et al., 2012). Older persons presenting more pronounced CLIP show indeed lower muscle mass and muscle strength; and are more likely to become frail. Elderly people possess an important residual, but latent, physical potential, which can be mobilized by training, even at very high ages (>90years). Physical exercise has also strong regulating and favourable effects on CLIP. Besides providing anabolic stimuli, it is well known that intensive physical training provokes an inflammatory reaction, accompanied by the liberation of pro-inflammatory cytokines (especially IL-6) and complex changes in the cellular components of the immune system. In this context, IL-6 is thought to be mainly released from the contracting muscles and would act as a "myokine", exerting a different function from that seen during e.g. acute infections. The acute phase response to exercise is positively related to the intensity of the muscle work delivered. Recently, it has been shown that older persons, similar to young adults, are able to respond to physical stress by a significant exercise-induced increase of circulating IL-6 (Bautmans et al., 2005). In fact, the exposure to (repetitive) mild stress has been shown to improve survival and longevity both at the cellular and organism level. In this context, an improved wound healing by physical training, has recently been described in old mice and in older humans; the underlying mechanisms, possible immune-related, have not been elucidated yet. Exercise can probably lower infection-induced cytokine release by peripheral mononuclear blood cells. Physical exercise would thus reduce sarcopenia as well as CLIP and the acute inflammatory response upon infection in the aged; thus enlarging considerably the scope of geriatric rehabilitation professionals in designing health-enhancing physical exercise programs. To date, however, optimal dosage of exercise to obtain most beneficial effects remains elusive, and more research is warranted to unravel the exact dose-response relationship.