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Exercise and bone mineral density in mature female athletes
J E Dook1, C James, N K Henderson
1Department of Human Movement, Edith Cowan University, Joondalup, WESTERN AUSTRALIA. jdook@cyllene.uwa.edu.au
Abstract:
An understanding of the relationship between weight-bearing activity and bone mineral density (BMD) is important in devising strategies to maximize and maintain skeletal strength in the female population, particularly those entering menopause. Three contrasting groups (N = 20) of mature female athletes (42-50 yr) with long-term (> 20 yr) histories of significant training and performance in their chosen sport were studied cross-sectionally. The groups were: (i) high impact sport (netball/basketball; HIGH), (ii) medium impact sport (running/field hockey; MED) and (iii) a nonimpact sport (swimming; NON) and (iv) a nonsport control group (CON; N = 20). Whole body and regional BMD and body composition (fat and lean mass) were measured by dual-energy x-ray absorptiometry. Isometric strength of dominant arm flexors and leg extensors was measured by a strain tensiometer. With an alpha level of significance of 0.05, HIGH showed significantly greater whole body and regional leg BMD than NON or CON. MED registered higher values than CON for whole body and regional leg BMD. Only HIGH had significantly greater leg strength than CON. Regional arm BMD was significantly greater in all exercising groups compared with CON, but no significant difference in arm strength was found between any groups. The athletic groups all had significantly lower body fat and higher height-corrected lean mass than CON. Height-corrected lean mass, height and leg extensor strength, but not calcium intake, arm flexor strength or body fat, were significant predictors of whole body and regional arm and leg BMD. Using the significant predictors as covariates, the impact groups (HIGH/MED) had significantly higher whole body BMD than CON. HIGH also had significantly higher whole body BMD than NON and both impact groups were greater than NON in regional leg BMD. Results suggest that females who participate regularly in the premenopausal years in high impact physical activity tend to have higher BMD than nonathletic controls.