Peak oxygen uptake reference equations for cycle ergometry based on body composition estimates

Background The measurement of peak oxygen uptake (VO2peak) using cardiopulmonary exercise testing (CPET) is the gold standard assessment of cardiorespiratory fitness (CRF). Although current VO2peak predictive equations usually consider weight or body mass index (BMI), body composition could provide further anthropometric contribution to CRF interpretation. Purpose To derive sex-specific VO2peak reference equations for cycle ergometer CPET that integrate estimated lean body mass (eLBM) and body fat percentage (eBF). Methods We pooled data from the "Flemish Study on Environment, Genes and Health Outcomes" (FLEMENGHO, Belgium), the "Integrative computer modeling for personalized profiling of CRF" (iCOMPEER, Belgium), and the "Fitness Registry and the Importance of Exercise: A National Database" (FRIEND, United States) cohorts. We selected apparently healthy adults who performed CPETs with a peak respiratory exchange ratio≥1.05 and a percent-predicted heart rate>80%. The National Health and Nutrition Examination Survey equations were used to calculate eLBM and eBF. Per subgroup of sex, age and BMI, 70% of the data was used for training the equations and 30% for testing them. Mixed regression models were applied, accounting geographic location as a random effect. The Wasserman and the Study of Health in West Pomerania (SHIP) equations were used for comparison[1,2]. Results The cohort consisted of 2203 females (681 from Belgium, 1522 from FRIEND) and 1342 males (395 from Belgium, 947 from FRIEND) as presented in Table 1. The resulting reference equation for females was VO2peak,females[mL/min] = 1329.6 + 34.2×eLBM(kg) - 24.1×eBF(%) - 0.122×age². In the training set, the mean absolute VO2peak error (MAE) was 209.7 mL/min; in the test set, MAE=218.7 mL/min (~0.84 metabolic equivalents [METs]). For males, the derived equation was VO2peak,males[mL/min] = 1984.3 + 50.1×eLBM(kg) - 78.8×eBF(%) - 0.101×age². In the training set, MAE was 333.4 mL/min; in the test set, MAE=359.6 mL/min (~1.16 METs). Overall, percent-predicted VO2peak (%pVO2peak) based on the proposed equations presented a good calibration (medians around 100%) among subgroups (Figure 1). In comparison, %pVO2peak calculated using the Wasserman equations generally provided a stable median (mostly between 90% and 95%) for females whereas larger differences across subgroups were observed for males. The SHIP equations presented relatively close %pVO2peak to our equation in the normal and overweight subgroups for males, but substantially lower %pVO2peak were observed for females at older ages across all BMIs. Conclusion The proposed equations allowed calibrated comparisons of an individual’s CRF to that of healthy individuals matched by sex, age and body composition (as an alternative to comparing to young adults with normal weight). This kind of comparison might be valuable in clinical practice with the increased life expectancy, prevalence of obesity, and weight loss medication users.For image description, please refer to the figure legend and surrounding text. For image description, please refer to the figure legend and surrounding text.