Abstract Background/aims Decreased cardiorespiratory fitness (CRF) is an all-cause mortality predictor. Oxygen consumption at peak exercise (VO2max) during a cardiopulmonary exercise test (CPET) is the gold standard for its evaluation. Since cardiometabolic risk factors reduce CRF, we aimed to assess the cardiopulmonary and metabolic responses during CPET and evaluate their determinants. Methods Subjects underwent incremental treadmill CPET and bioelectrical impedance analysis. Insulin sensitivity was estimated using the HOMA, QUICKI, and METS-IR indices. Multivariate regressions were used to evaluate determinants of VO2max. Nonlinearity was confirmed with an F-test between linear and polynomial models. Results 503 subjects were evaluated, 474 met maximum effort criteria, (64% females). Median age was 4(26-52). 41% had normal weight, 33% overweight, 26% obesity. Prevalence of insulin resistance ranged from 22% to 46%, depending on the equation used. VO2max was 29.8(24-36) and 36.6 (30.6-43.3) mL/kg/min for females and males. Body composition analysis revealed that a higher BMI exhibited strong biological collinearity with metrics associated with adiposity excess and was inversely associated with CRF. After adjusting for age, sex, BMI, and fat mass, insulin resistance evaluated by QUICKI explained up to 43% of VO2max variability and was inversely associated with CRF. Conclusions In a cohort of individuals without established CVD, the main determinants of CRF were modifiable risk factors associated with excess adiposity and insulin resistance. The potential mechanisms underlying the reduction in CRF include decreased relative muscle mass and insulin resistance, which reduces muscle glucose uptake and O2 consumption during maximum effort, where anaerobic glycolysis plays a central role.
Muñoz-Hernández et al. (2026) studied this question.