Comparing individual and population differences in minute ventilation/carbon dioxide production slopes using centile growth curves and log-linear allometry

Identifying vulnerable groups and/or individuals’ cardiorespiratory fitness (CRF) is an important challenge for clinicians/researchers alike. To quantify CRF accurately, the assessment of several variables now standard practice including maximal oxygen uptake ( V ʹ CO 2 ) and ventilatory efficiency, latter assessed using minute ventilation/carbon dioxide production E / slope. Recently, reference values (centiles) slopes males females aged 20 to 80 have been published, cardiopulmonary exercise testing (CPX) data (treadmill protocol) from Fitness Registry Importance Exercise National Database (FRIEND Registry). In current observational study we provide centile curves FRIEND slopes, fitted generalised additive model location, scale shape (GAMLSS), individuals with a more precise estimate where their fall within population. We also confirm that by adopting allometric models (incorporating log transformation), resulting ANCOVAs provided normal homoscedastic residuals, superior goodness-of-fit Akaike information criterion (AIC)=14 671 (compared traditional ANCOVA's AIC=15 008) confirms are vastly ANCOVA models. conclusion, providing sex-by-age rather than referring tables efficiency slopes) will accurate estimates individual's particular slope falls Also, researchers likely identify real valid inferences when analysing population/group differences in slopes.