Estimating VO 2peak in 18-90 Year-Old Adults: Development and Validation of the FitMáx©-Questionnaire

Cardiorespiratory fitness (CRF) plays an essential role in health outcomes and quality of life. However, it is often not assessed nor estimated. Objective CRF assessment is costly, labour intensive and not widely available. Patient-reported outcome measures estimate CRF more cost-efficiently, but current questionnaires lack accuracy. The aim of this study is to develop a new self-reported questionnaire to estimate CRF. The FitMáx©-questionnaire, consisting of only three questions assessing walking, stair climbing, and cycling capacity, was compared with the commonly used Duke Activity Status Index (DASI) and Veterans Specific Activity Questionnaire (VSAQ). These questionnaires were compared to peak oxygen uptake (VO ) as measured with cardiopulmonary exercise testing. This study included 759 cardiac, pulmonary and oncologic patients and healthy persons aged 18‒90. FitMáx© strongly correlated (r = 0.94 (0.92‒0.95) SEE = 4.14 mL∙kg ∙min ) with measured VO . Bias between predicted and measured VO was -0.24 (-9.23‒8.75; 95% limits of agreement) mL·kg ·min . The FitMáx© scored superiorly on correlation and SEE compared with the DASI and VSAQ, r = 0.75 (0.68‒0.80) SEE = 4.62 mL∙kg ∙min and r = 0.87 (0.83‒0.90) SEE = 6.75 mL∙kg ∙min , respectively. FitMáx© is a valid and accessible questionnaire to estimate CRF expressed as VO in clinical practice and shows substantial improvement compared to currently used questionnaires.