Low Energy Availability And The Female Athlete Triad In Endurance Athletes Versus Controls

Abstract

The Female Athlete Triad is defined as the interrelatedness of the spectra of energy availability, menstrual function and bone health. Low energy availability (EA) has not been studied extensively and has never been compared between athletes and controls. PURPOSE: To compare EA between athletes and controls and examine its relationship to other Triad components. METHODS: Twenty female endurance athletes (age: 29.4±4.7y) and 12 normally active women (age: 29.9±5.3y; exercise ≤5 hrs/wk) completed a questionnaire assessing disordered eating, menstrual function, training history and injury. Energy availability was calculated from three 24-hour dietary and physical activity recalls using the Compendium for Physical Activities (Ainsworth et al., 2000). These data were cross-validated by digital photographs and subjects' food intake and exercise logs. Areal bone mineral density (aBMD) was measured at the femoral neck, total femur, lumbar spine and whole body by DXA. Descriptive statistics were calculated and group comparisons were analyzed by independent t-tests, Pearson's Product Moment correlations and Chi-Square. RESULTS: Mean EA did not significantly differ between athletes (37.2±19.3 kcal·kg-1FFM·d-1) and controls (40.5±14.3 kcal·kg-1FFM·d-1; p=0.62). Low EA was similar between athletes (37%; n=7) and controls (36%; n=4). In both groups, 2 subjects met the criteria for the full triad. 85% of athletes (n=17) had at least one Triad component compared with 67% (n=8) in controls. Low bone mass (Z score < -1.0) was found in 30% of athletes (n=6) and 17% of controls (n=2). Mean lumbar spine aBMD scores tended to be lower in athletes (1.164±0.125g/cm2) than in controls (1.245±0.131g/cm2; p=0.05). Athletes reporting an older age at menarche were more likely to have low EA (r=-0.50, p=0.02), and lower Z-scores at the femoral neck (r= -0.53, p= 0.02) and total femur (r= -0.48, p=0.04). In contrast, these relationships were not statistically significant in controls. In contrast, these relationships were not statistically significant in controls. CONCLUSION: Our results confirm that the full Triad and low EA exist in both athletes and controls but that endurance athletes are at greater risk for low bone mass than normally active women.