The type and intensity of exercise have independent and additive effects on bone mineral density

Previous research on the effects of running and swimming on areal bone mineral density (aBMD) is inconclusive. This study examined the putative roles of the type and intensity of exercise in this respect, by measuring aBMD (adjusted for age, weight, and height) of the total body and of various subregions in 52 males aged 17 - 30 yr (21 runners, 16 swimmers, 15 controls). The athletes were competing at either long-distance ("endurance", n = 17) or short-distance ("sprint", n = 20) events. Compared with controls, runners had significantly higher leg aBMD (+ 6.7 %, p < 0.05), while swimmers had significantly lower leg and total body aBMD (- 9.8 % and - 7.0 %, respectively, p < 0.05). Endurance athletes had significantly lower total body aBMD than controls (- 4.9 %, p < 0.05). Sprint athletes did not differ significantly from controls at any site, but they had significantly higher aBMD than endurance athletes throughout the skeleton (p < 0.05). Compared with controls, endurance swimmers had significantly lower aBMD at the legs and total body (- 14.8 % and - 10.4 %, respectively, p < 0.05), while sprint runners had significantly higher values for the legs, trunk, and total body (+ 8.0 %, + 10.0 %, and + 6.3 %, respectively, p < 0.05). Sprint swimmers and endurance runners did not differ from controls at any site or the total body. These results suggest that the type and intensity of exercise have independent and additive effects on bone density.