Bone Abstracts

Mechanical loading exerts a major influence on the size, shape and structure of the skeleton attained in early adulthood, an important determinant of osteoporotic fracture risk in later life. In studies of exercise interventions in children intended to optimise skeletal development, activities associated with relatively high impacts are generally more effective, in line with findings from laboratory studies that bone is exquisitely sensitive to high impacts producing transient skeletal deformation. Epidemiological studies have sought to explore these relationships at different periods, based on a range of methods for evaluating loading and bone development. Recent studies have highlighted the role played by mechanical loading in early life. For example, breech position in the last trimester, which constrains fetal limb movement, is associated with reduced neonatal whole body mass, reduced hip bone mass at age 4, and reduced tibial cortical bone mass at age 17. In addition, we recently found that males born to mothers with oligohydramnios have relatively narrow hips at age 17, ascertained by statistical shape modelling applied to DXA scans. Mechanical loading has also been examined in infancy, as illustrated by findings that age of walking is related to hip strength at age 63, and motor development assessed at age 18 months to hip strength at age 17. Another important focus has been the study of relationships between physical activity, assessed by 7 day accelerometry, and bone development in later childhood. For example, greater participation in vigorous physical activity was associated with greater tibial cortical bone mass at age 15, whereas an equivalent benefit was not seen with moderate activity. Subsequent findings suggest these benefits may be related to the number of bouts of vigorous activity, as opposed to total duration of activity. In further studies, using a device to record impacts within specific g-bands, impacts greater than 4 g (equivalent to running at > 10 km/hour) were found to be associated with greater hip strength and tibial cortical bone mass. Questionnaire based approaches have also been successfully applied, exemplified by positive associations between participation in sporting activity in young adulthood and tibial cortical bone size in men aged 80 years. Taken together, epidemiological studies suggest that mechanical loading plays an important role in bone development, leading to long lasting benefits for skeletal health.

Disclosure: The author declared no competing interests.

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