ABSTRACT
Physical activity is known to have an anabolic effect on bone tissue. It has been shown to increase the bone mineral density (BMD) in young and middle-age adults, as well as in teenagers[1]. The type, intensity and duration of exercise necessary to influence BMD in humans is well documented in adults. Thus, sport activities including heavy load, or producing impact loading on the skeleton, are associated with higher bone density than sports which do not generate stress on the skeleton. But few studies refer to human subjects involved in swimming, particularly in childhood, despite the attractiveness of swimming as a non-traumatic activity. However, some researchers have shown that physical activity in childhood was an important determinant of peak bone mass in women[2]. Moreover, the prepubertal period is an important stage of growing in children because the optimal period of bone turnover is, in female, over a period from 11 to 14 y of age[2-3]. Most of the studies have investigated BMD or bone mineral content (BMC) in female subjects. However, the resistance of bone tissue is influenced by bone density and by trabecular bone microarchitecture. The growing period, when the bone mineral acquisition is at the optimal phase, could be particularly sensitive to this phenomenon. Thus, studies dealing with the relationship between physical activity and bone metabolism have to investigate, not only bone mineralization parameters, but also bone architecture parameters. The purpose of this study was to compare the effects of 3 y of intensive sport training on the bone status (bone density and architecture) in a group of elite prepubertal girls, at the starting period of their peak bone mass acquisition. These girls were engaged either in sport requiring significant impact loading on the skeleton (gymnastics), or in sport without impact loading (swimming). These results are the first of a longitudinal study which will be conducted over the pubertal period.
