PHYSICAL ACTIVITY PREDICTS BONE MEASURES IN YOUNG CHILDREN

Abstract

Previous research indicates that physical activity (PA) has a beneficial effect on bone development in circumpubertal children, though its effect on younger children is uncertain. We examined cross-sectional associations between PA and bone measures in 368 young children (mean age 5.2 yr, range 4 to 6 yr). PA was measured using 4-d accelerometry readings, parental report of children's usual PA compared to peers, and parental report of children's hours of daily television viewing. Total body and site-specific bone mineral content (BMC) and area bone mineral density (BMD) were measured by dual energy x-ray absorptiometry. After adjustment for age and body size, accelerometry measures of PA and parental report of usual PA were consistently and positively associated with BMC and BMD in both boys and girls (r = 0.15 to 0.28). In regression analyses, after adjustment for age and body size, at least one and often several of the PA variables entered as independent predictors of bone measures for both boys and girls in all models except total body. Findings indicate that significant and, perhaps, important increases in bone measures may result from increases in PA during early childhood, well ahead of the onset of peak bone mass development sometime after puberty. Supported by NIH RO1 DE12101, R01 DE09551 and RR00059 from the General Clinical Research Centers Program, NCRR, NIH.