The Effect of Weight-Bearing Exercise on Bone Mineral Density: A Study on Female Ex-Athletics and the General Population

Dr. John Ethefington, London
St Thomas Hospital , London

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 athletes (67 middie and long distance runners, 16 tennis players, currently aged 40-65) were recruited from the original records of their sporting associations. Controls were 585 age matched females. The main outcome measures were BIVID of lumbar spine (LS) femoral neck (FN) and forearm, estimated by DXA scan. Levels of physical activity were assessed using a modified Allied Dunbar Fitness Survey scale and classified as a) Ex-athletes b)

Active controls ( > 1 hour of vigorous physical activity currently and in the past) c) Low activity controls with inconsistent or intermediate levels of activity d) Inactive controls (<15 minutes exercise per week). Results: after adjustment for differences in age, weight, height and smoking, athletes had greater BIVIDs than controls; 8.7% at the LS (95% CI 5.4 – 12.0, p< 0.001) and 12.1% at FN (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 BIVIDs than the Inactive group (n = 347) : 7.9% LS (2.0 – 13.8, p = 0.009) and 8.3% FN (2.7 – 13.8, p = 0.004). The Low activity controls (n = 216) had an intermediate BMD. Tennis players had greater BMDs compared to runners; 12.0% LS (5.7 – 18.2 p = 0.0004), 6.5 % FN (- 0.2 – 13.2, p = 0.066). The BIVID of Tennis players’ dominant forearms were greater than their non-dominant forearms. In conclusion, regular vigorous weight bearing exercise of one hour or more per week is associated with an increase in BIVID within a normal population. This study confirms long term weight-bearing exercise as an important factor in the regulation of bone mass and fracture prevention.