title: [Exercise and bone mineral density in old subjects: theorical and practical implications].
abstract: With age advancement, the decrease of bone mineral density is ineluctable. Physical exercise constitutes a physiological approach likely to attenuate or limit the effects of normal bone demineralization (i.e. not pathological) particularly in elderly subjects. Indeed, physical exercise induces mechanical constraints generating bone deformation which stimulates osteogenesis and favors bone remodelage. Physical activities achieved in condition of body discharge (e.g. swimming, cycling) or in static condition (e.g. stretching, balance) do not stimulate (or very weakly) osteogenesis. The osteogenic function of aerobic training (e.g. walking, running) is effective only if the intensity of exercise is high (i.e. the impacts on the ground and thus the bone deformation) and that of strength training is effective only if the completed muscular contractions are dynamic and carried out with heavy loads. The calcium concentration increase is greater on the concave side than on the convex side for the bones which undergo strong mechanical pressures during exercise. Hence, it is advisable to vary the directions of mechanical constraints during physical activity to strengthen the resistance of the bone in all the plans. In order to obtain significant effects in terms of bone remodelage, the optimal duration of training programs should last at least 4 to 6 months. The osteogenic effects of regular exercise begin from 2-3 weekly sessions. The activation of osteogenesis by means of physical exercise is more difficult in aging women than in aging men because of hormonal factors that are not favorable in aging women. At last, regular exercise is fundamental not only to maintain bone mineral density but also to reduce the risk of bone fracture since there is a relationship between the bone mineral density and the risk of bone fracture.
authors.affiliation: Laboratoire activité physique performance et santé (Upres EA 4445), Université de Pau & Pays de l'Adour, Département Staps de Tarbes, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Paillard
mesh_terms: D000368:Aged; D000375:Aging; D015519:Bone Density; D015444:Exercise; D006801:Humans; D010012:Osteogenesis
keywords: amount of physical activity; bone mineral density; elderly subjects; physical exercise; risk of fracture