Impact exercise increases BMC during growth: an 8-year longitudinal study

Abstract

Our aim was to assess BMC of the hip over 8 yr in prepubertal children who participated in a 7-mo jumping intervention compared with controls who participated in a stretching program of equal duration. We hypothesized that jumpers would gain more BMC than control subjects. The data reported come from two cohorts of children who participated in separate, but identical, randomized, controlled, school-based impact exercise interventions and reflect those subjects who agreed to long-term follow-up (N = 57; jumpers = 33, controls = 24; 47% of the original participants). BMC was assessed by DXA at baseline, 7 and 19 mo after intervention, and annually thereafter for 5 yr (eight visits over 8 yr). Multilevel random effects models were constructed and used to predict change in BMC from baseline at each measurement occasion. After 7 mo, those children that completed high-impact jumping exercises had 3.6% more BMC at the hip than control subjects whom completed nonimpact stretching activities (p < 0.05) and 1.4% more BMC at the hip after nearly 8 yr (BMC adjusted for change in age, height, weight, and physical activity; p < 0.05). This provides the first evidence of a sustained effect on total hip BMC from short-term high-impact exercise undertaken in early childhood. If the benefits are sustained into young adulthood, effectively increasing peak bone mass, fracture risk in the later years could be reduced.

FIG. 1

Jumping intervention effect on Δτotal hip BMC after 8 yr. Percent change in total hip BMC in jumpers above that of controls after 7 mo of exercise training, 1 yr of detraining (19 mo), and 4–8 yr of detraining (43–91 mo). The intervention participants had 3.6% greater bone mass than controls immediately after the intervention and 1.4% greater bone mass at the total hip than controls after 8 yr. *Results are adjusted for baseline age, ΔHt, ΔWt, maturity, and sports participation and are significant at each of the seven measurement intervals (p < 0.05).