Endocrine Abstracts

Background: Cardiorespiratory fitness is a measure for physical activity and a prognostic health indicator. However, measurement of maximal oxygen consumption (VO2max) is not possible in clinical practice.

Aim: We hypothesized that body composition and testosterone levels could be used as possible determinants of VO2max in young men.

Participants and design: The Odense Androgen Study, a population-based, observational study including 780 men aged 20–30 years. VO2max (ml/min/kg 0.73) was indirectly measured by a mechanically braked cycle ergometer. Fat mass (%) and lean body mass (%) were assessed by whole-body DXA scans. Total testosterone levels (nmol/l) were measured (RIA using extraction and chromatography). SHBG levels (nmol/l) were determined by immunoluminometric assay. Bioavailable and free testosterone were calculated.

Results: Descriptive data of the subjects were BMI 24.4 kg/m² (22.4–26.6), waist 88 cm (82–94), percentage lean body mass 79.1% (75.6–82.5), percentage fat mass 17.2% (18.8–21.1), total testosterone 20.7 nmol/l (17.0–25.4), SHBG 27 nmol/l (21–34) and VO2max 160.3 ml/min/kg 0.73 (143.3–177.6) (median (interquartile range). In bivariate analysis, lean body mass (%) (r=0.62), SHBG (r=0.26), total testosterone (r=0.24), and free testosterone (r=0.13) were positively associated with VO2max, whereas fat mass (%) (r=−0.63) and waist (r=−0.47) were negatively associated with VO2max (all P<0.001). Fat mass (%) and lean body mass (%) were closely associated (r=−0.998, P<0.001). In multivariate regression analysis, models with VO2max as the dependent variable and lean body mass (%) or fat mass (%) as independent variables were the best predictors of VO2max (both models R2=0.47), whereas the models including testosterone (total, free or bioavailable testosterone) or SHBG as independent variables had lower R2 values (R2=0.09–0.13). All models were adjusted for age and smoking.

Conclusion: Body composition measures were the best predictors of VO2max in young men. VO2max was more closely associated with waist than testosterone or SHBG.