Bone and Muscles

Abstract

A reduction of muscle and bone mass and an increase in fat mass are characteristic changes in increasing age. The term “sarcopenia” includes an age-related loss of muscle mass and muscle strength. Muscle loss also significantly contributes to the development of various metabolic and mechanical geriatric syndromes (e.g., diabetes type 2). Sarcopenia develops from the age of 35 years and leads above all to a decline in type II muscle fibres and an increase of intramuscular lipids. The skeletal muscle also produces various growth factors (IGF-1 and MGF), which have an anabolic effect on the skeleton and also support fracture healing. These “myokines” are above all demonstrably increased by muscle building training. In contrast, during physical inactivity and muscular atrophy, myostatin, a negative regulator of muscle mass, leads to muscle loss. Other factors that lead to a decrease in muscle strength and muscle mass include cachexia, AIDS, smoking, protein and vitamin D deficiency, chronic inflammatory processes (e.g. COPD) and glucocorticoids. In addition to sarcopenia, intramuscular lipid, “myosteatosis”, increases with age and increasing body fatness.