Growing bones: how important is exercise?

Purpose of review: The aim of this review is to summarize what is known about the relationship between childhood physical activity and bone mineral mass, bone geometry and bone strength. Recent findings: A number of studies consistently show a beneficial effect of childhood physical activity on bone mineral accretion. Recent data suggest that hormonal milieu, stage of maturation and the type of activity influence how much and where (periosteal or endocortical surfaces) new bone is laid down in response to loading. Individuals who are consistently active during adolescence reach adulthood with better bone geometry, and greater bone strength. Pre and early puberty are an opportune time to introduce osteogenic activities. Summary: It is clear (in our opinion) that mechanical loading dominates bone adaptation during growth, and other factors such as nutrition, disease and hormonal milieu may mediate the effect. The exact prescription for optimal bone development is not yet clearly defined, but activities that induce moderate to high-impact with fast strain rates in unusual patterns have a positive effect on bone development, even with only a few loading cycles. Inserting rest between activity bouts has promise as a means of optimizing the bone response to loading in brief period