Reference equations for peak oxygen uptake for treadmill cardiopulmonary exercise tests based on the NHANES lean body...

Cardiorespiratory fitness (CRF), measured by peak oxygen uptake (VO2peak), is a strong predictor of mortality. Despite its widespread clinical use, current reference equations for VO2peak show distorted calibration in obese individuals. Using data from the Fitness Registry and the Importance of Exercise National Database (FRIEND), we sought to develop novel reference equations for VO2peak better calibrated for overweight/obese individuals-in both males and females, by considering body composition metrics.

Graded treadmill tests from 6836 apparently healthy individuals were considered in data analysis. We used the National Health and Nutrition Examination Survey equations to estimate lean body mass (eLBM) and body fat percentage (eBF). Multivariable regression was used to determine sex-specific equations for predicting VO2peak considering age terms, eLBM, and eBF. The resultant equations were expressed as VO2peak (male) = 2633.4 + 48.7 × eLBM (kg) - 63.6 × eBF (%) - 0.23 × Age2 (R2 = 0.44) and VO2peak (female) = 1174.9 + 49.4 × eLBM (kg) - 21.7 × eBF (%) - 0.158 × Age2 (R2 = 0.53). These equations were well-calibrated in subgroups based on sex, age, and body mass index (BMI), in contrast to the Wasserman equation. In addition, residuals for the percent-predicted VO2peak (ppVO2) were stable over the predicted VO2peak range, with low CRF defined as <70% ppVO2 and average CRF defined between 85 and 115%.

The derived VO2peak reference equations provided physiologically explainable and were well calibrated across the spectrum of age, sex, and BMI. These equations will yield more accurate VO2peak evaluation, particularly in obese individuals.