THE EFFECT OF WEIGHT-BEARING EXERCISE ON BONE-MINERAL DENSITY - A STUDY OF FEMALE EX-ELITE ATHLETES AND THE GENERAL-POPULATION

The aim of this retrospective cohort study was to estimate the changes in bone mineral density (BMD) as a consequence of exercise in female ex-athletes and age-matched controls. Eighty-three ex-elite female ath letes (67 middle and long distance runners, 16 tennis players, current ly aged 40-65) were recruited from the original records of their sport ing associations, Controls were 585 age-matched females, The main outc ome measures were BMD of lumbar spine (LS), femoral neck (FN), and for earm, estimated by dual-energy X-ray absorptiometry (DXA) scan, Levels of physical activity were assessed using a modified Allied Dunbar Fit ness Survey scale and classified as (a) ex-athletes, (b) active contro ls (greater than or equal to 1 h of vigorous physical activity current ly and in the past), (c) low activity controls with inconsistent or in termediate levels of activity, and (d) inactive controls (< 15 minutes of exercise per week), After adjustment for differences in age, weigh t, height, and smoking, athletes had greater BMDs than controls: 8.7% at the LS (95% confidence interval [CI] 5.4-12.0; p < 0.001) and 12.1% at FN (CI 9.0-15.3; p < 0.001), The benefits of exercise appeared to persist after cessation of sporting activity, Active controls (n = 22) had greater BMDs than the inactive group (n = 347): 7.9% LS (CI 2.0-1 3.8; p = 0.009) and 8.3% FN (CI 2.7-13.8; p = 0.004), The low activity controls (n = 216) had an intermediate BMD, Tennis players had greate r BMDs compared with runners: 12.0% LS (CI 5.7-18.2; p = 0.0004) and 6 .5% FN (CI -0.2-13.2; p = 0.066), The BMD of tennis players' dominant forearms were greater than their nondominant forearms, In conclusion, regular vigorous weight-bearing exercise of 1 h or more per week is as sociated with an increase in BMD within a normal population, This stud y confirms long-term weight-bearing exercise as an important factor in the regulation of bone mass and fracture prevention.