To evaluate the effects of a 12-month exercise intervention using either high-impact step aerobic exercise or moderate-intensity strength training on areal bone mineral density (aBMD) we studied 51 untrained women, aged 20 to 35 years, for this study. Whole body and heel and wrist aBMD were measured by dual-energy x-ray absorptiometry (DXA, Hologic or PIXI Lunar). Subjects were randomly assigned to: impact-loaded step aerobic exercise (SA, n = 15), moderate-intensity lower body strength training (ST, n = 16) or non-exercise control (CON, n = 20). Data analysis only included those who completed 95% of each training routine and attended at least 80% of all sessions. Group differences in aBMD, leg press strength and urinary cross-link deoxypridinoline (DPD) were analysed using analysis of variance. After a 12-month intervention, the SA elicited an increase in aBMD of the heel (4.4%, p < 0.05) and leg press strength (15%, p < 0.05), relative to baseline. Meanwhile, the ST showed an increase in leg press strength (48%, p < 0.05) with no significant increase in aBMD at any measured site. Similar and unchanged DPD was observed in all 3 groups at baseline, 6 and 12 months. In conclusion, a 12-month high-impact step aerobic exercise resulted in a significant increase in the heel aBMD in untrained young women, who complied with the exercise regimen. A moderate intensity strength training intervention of similar duration had no effect on aBMD although leg strength increased significantly.

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