PRE-MENOPAUSAL AND POSTMENOPAUSAL WOMEN HAVE DIFFERENT BONE-MINERAL DENSITY RESPONSES TO THE SAME HIGH-IMPACT EXERCISE

The effects of a vertical jumping exercise regime on bone mineral dens ity (BMD) have been assessed using randomized controlled trials in bot h pre- and postmenopausal women, the latter stratified for hormone rep lacement therapy (HRT), Women were screened for contraindications or m edication likely to influence bone. The premenopausal women were at le ast 12 months postpartum and not lactating; the postmenopausal women h ad been stable on, or off, HRT for the previous 12 months and througho ut the study. BMD was measured blind using dual-energy X-ray absorptio metry at the spine (L2-L4) and the proximal femur. The exercise consis ted of 50 vertical jumps on 6 days/week of mean height 8.5 cm, which p roduced mean ground reactions of 3.0 times body weight in the young wo men and 4.0 times in the elder women. Ire the premenopausal women, the exercise resulted in a significant increase of 2.8% in femoral BMD af ter 5 months (p < 0.001, n = 31), This change was significantly greate r (p < 0.05) than that found in the control group (n = 26), In the pos tmenopausal women, there was no significant difference between the exe rcise and control groups after 12 months (total n = 123) nor after 18 months (total n = 38), HRT status did not affect this outcome, at leas t up to 12 months, Pt appears that premenopausal women respond positiv ely to this brief high-impact exercise but postmenopausal women do not .