Jump starting skeletal health: a 4-year longitudinal study assessing the effects of jumping on skeletal development in pre and circum pubertal children.

Introduction: Evidence suggests bone mineral increases attributable to exercise training prior to puberty may confer a significant advantage into adulthood. However, there is a dearth of supportive prospective longitudinal data. The purpose of this study was to assess bone mineral content (BMC) of the whole body (WB), total hip (TH), femoral neck (FN) and lumbar spine (LS) over four years in pre-pubertal boys and girls following a 7-month jumping intervention.

Methods: The study population included 107 girls and 98 boys aged 8.6+/-0.88 years at baseline. Participating schools were randomly assigned as either intervention or control school. Children at the intervention school (n=101) participated in a jumping intervention embedded within the standard PE curriculum. The control school children (n=104) had similar exposure to PE without the jumping intervention. BMC was assessed by DXA at baseline, at 7-month post intervention, and annually thereafter for three years totaling 5 measurement opportunities. Multi-level random effects models were constructed and used to predict change from study entry in BMC parameters at each measurement occasion.

Results: A significant intervention effect was found at all bone sites. The effect was greatest immediately following the intervention (at 7 months) but still significant three years after the intervention. At 7 months, intervention participants had BMC values that were 7.9%, 8.4%, 7.7% and 7.3% greater than the controls at the LS, TH, FN and WB, respectively (p<0.05), when the confounders of age, maturity and tissue mass were controlled. Three years after the intervention had concluded the intervention group had 2.3%, 3.2%, 4.4% and 2.9% greater BMC than controls at the LS, TH, FN and WB respectively (p<0.05), when the confounders of age, maturity and tissue mass were controlled.

Conclusions: This provides evidence that short-term high impact exercise in pre-puberty has a persistent effect over and above the effects of normal growth and development. If the benefits are sustained until BMC plateaus in early adulthood, this could have substantial effects on fracture risk.