Jumping improves hip and lumbar spine bone mass in prepubescent children: A randomized controlled trial

Physical activity during childhood is advocated as one strategy for enhanci ng peak bone mass (bone mineral content [BMC]) as a means to reduce osteopo rosis-related fractures. Thus, we investigated the effects of high-intensit y jumping on hip and lumbar spine bone mass in children. Eighty-nine prepub escent children between the ages of 5.9 and 9.8 years were randomized into a jumping (n = 25 boys and n = 20 girls) or control group (n 26 boys and n = 18 girls). Both groups participated in the 7-month exercise intervention during the school day three times per week. The jumping group performed 100 , two-footed jumps off 61-cm boxes each session, while the control group pe rformed nonimpact stretching exercises. BMC (g), bone area (BA; cm(2)), and bone mineral density (BMD; g/cm(2)) of the left proximal femoral neck and lumbar spine (L1-L4) were assessed by dual-energy X-ray absorptiometry (DXA ; Hologic QDR/4500-A). Peak ground reaction forces were calculated across 1 00, two-footed jumps from a 61-cm box. In addition, anthropometric characte ristics (height, weight, and body fat), physical activity, and dietary calc ium intake were assessed. At baseline there were no differences between gro ups for anthropometric characteristics, dietary calcium intake, or bone var iables. After 7 months, jumpers and controls had similar increases in heigh t, weight, and body fat. Using repeated measures analysis of covariance (AN COVA; covariates, initial age and bone values, and changes in height and we ight) for BMC, the primary outcome variable, jumpers had significantly grea ter 7-month changes at the femoral neck and lumbar spine than controls (4.5 % and 3.1%, respectively). In repeated measures ANCOVA of secondary outcome s (BMD and BA), BMD at the lumbar spine was significantly greater in jumper s than in controls (2.0%) and approached statistical significance at the fe moral neck (1.4%;p = 0.1185). For BA, jumpers had significantly greater inc reases at the femoral neck area than controls (2.9%) but were not different at the spine. Our data indicate that jumping at ground reaction forces of eight times body weight is a safe, effective, and simple method of improvin g bone mass at the hip and spine in children. This program could be easily incorporated into physical education classes.