Abstract 4140399: The Importance of Measuring Body Composition in Determining Cardiorespiratory Fitness Across the Adult Age Range

Background: Maintaining cardiorespiratory fitness (CRF) is essential for healthy aging and is linked to lower risk of age-related cardiovascular diseases and frailty. However, the relations of body composition metrics and CRF levels across the adult age range are poorly understood. Hypothesis: Healthy body composition, characterized by higher lean mass and lower visceral and total adiposity, is associated with greater oxygen (O 2 ) uptake during exercise across age and sex. Aims: To investigate relations of components of body composition with O 2 uptake measures during exercise and to evaluate how age and sex affect the associations. Methods: Framingham Heart Study participants (n=2742) underwent dual-energy X-ray absorptiometry (DXA) for body composition assessment and maximal cardiopulmonary exercise testing on a cycle ergometer at the same exam cycle. Sex-stratified linear models between DXA and O 2 uptake measures were adjusted for age, height, HDL/total cholesterol, smoking, systolic blood pressure, hypertension treatment, diabetes, and physical activity index. Results: The study sample had a mean age of 54±9 years, was 54% women, 9% non-white, and had a peak O 2 uptake [VO 2 ] 95±20% of predicted. Higher lean mass was associated with higher peak VO 2 in ml/min in both men and women (β for standard deviation (SD) difference in log-transformed peak VO 2 for a 1-SD higher value of lean mass was 0.49 in men and 0.57 in women, P<0.0001 for both). Conversely, measures of total and visceral fat mass were associated with higher peak VO 2 in women (β= 0.14-0.15, P<0.0001) but not in men (P>0.05). The variance explained (adjusted R 2 ) in peak VO 2 was higher for lean mass than other DXA measures: lean mass, age, and height explained 45-47% of the variance in peak VO 2 in men and women, while age, height, and other DXA measures explained ≤37%. Furthermore, individuals with higher observed lean mass than predicted based on age, sex, and BMI had higher observed peak VO 2 , consistent with the finding that higher lean mass is associated with higher peak VO 2 across age and sex (Figure). Conclusion: Maintaining lean mass across the adult age range is linked with higher peak VO 2 , which may have important implications for promoting healthy aging.