Purpose 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. Materials and Methods 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 2peak ) as measured with cardiopulmonary exercise testing. This study included 759 cardiac, pulmonary and oncologic patients and healthy persons aged 18‒90. Results FitMáx© strongly correlated (r = 0.94 (0.92‒0.95) SEE = 4.14 mL∙kg −1 ∙min −1 ) with measured VO 2peak . Bias between predicted and measured VO 2peak was −0.24 (−9.23‒8.75; 95% limits of agreement) mL·kg −1 ·min −1 . 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 −1 ∙min −1 and r = 0.87 (0.83‒0.90) SEE = 6.75 mL∙kg −1 ∙min −1 , respectively. Conclusion FitMáx© is a valid and accessible questionnaire to estimate CRF expressed as VO 2peak in clinical practice and shows substantial improvement compared to currently used questionnaires.

Objectives: Cardiorespiratory fitness plays an essential role in health outcomes and quality of life. Objective assessment of cardiorespiratory fitness is costly, labour intensive and not widely available. Although patient-reported outcome measures estimate cardiorespiratory fitness more cost-efficiently, the current questionnaires lack accuracy. The aim of this study is to develop and validate the FitMáx©-questionnaire, a self-reported questionnaire to estimate cardiorespiratory fitness in healthcare. Methods: We developed the FitMáx©-questionnaire, consisting of three questions assessing walking, stair climbing, and cycling capacity. A comparison on estimating VO2peak was made with the Duke Activity Status Index (DASI), Veterans Specific Activity Questionnaire (VSAQ) and cardiopulmonary exercise testing as the gold standard. A total of 716 patients and athletes (520 men, 196 women) aged 18‒91 performed a CPET in our hospital. We randomly selected 70% of the subjects to fit a linear regression model to estimate VO2peak based on the FitMáx© scores. The remaining 30% of participants was used for validation of this model. Results: The VO2peak estimated by the FitMáx© strongly correlates with the VO2peak measured objectively with CPET; r=0.95 (0.93‒0.96) SEE=3.94 ml∙kg-1∙min-1. Bias between predicted and measured VO2peak was 0.32 ml·kg-1·min-1 and the 95% limits of agreement were -8.11 ‒ 9.40 ml∙kg-1∙min-1. In our sample, the FitMáx© scored superiorly on correlation and SEE compared with those from the DASI and VSAQ, r=0.80 (0.73‒0.86) SEE=4.22 ml∙kg-1∙min-1 and r=0.88 (0.84‒0.91) SEE=6.61 ml∙kg-1∙min-1, respectively. Conclusion: FitMáx© is a valid and accessible questionnaire to estimate cardiorespiratory fitness expressed as VO2peak and shows substantial improvement compared to currently used questionnaires.

Background Evaluating the criterion validity and responsiveness of the self-reported FitMáx©-questionnaire, Duke Activity Status Index (DASI) and Veterans Specific Activity Questionnaire (VSAQ) to monitor aerobic capacity in cancer survivors. Methods Cancer survivors participating in a 10-week supervised exercise program were included. The FitMáx©-questionnaire, DASI, VSAQ and a cardiopulmonary exercise test (CPET) were completed before (T0) and after (T1) the program. Intraclass correlation coefficients (ICC) were calculated between VO2peak estimated by the questionnaires (questionnaire-VO2peak) and VO2peak measured during CPET (CPET-VO2peak), at T0 to examine criterion validity, and between changes in questionnaire-VO2peak and CPET-VO2peak (ΔT0-T1) to determine responsiveness. Receiver operating characteristic (ROC) analyses were performed to examine the ability of the questionnaires to detect true improvements (≥ 6%) in CPET-VO2peak. Results Seventy participants were included. Outcomes at T1 were available for 58 participants (83%). Mean CPET-VO2peak significantly improved at T1 (Δ1.6 mL·kg− 1·min− 1 or 8%). Agreement between questionnaire-VO2peak and CPET-VO2peak at T0 was moderate for the FitMáx©-questionnaire (ICC = 0.69) and VSAQ (ICC = 0.53), and poor for DASI (ICC = 0.36). Poor agreement was found between ΔCPET-VO2peak and Δquestionnaire-VO2peak for all questionnaires (ICC 0.43, 0.19 and 0.18 for the FitMáx©-questionnaire, VSAQ and DASI, respectively). ROC analysis showed that the FitMáx©-questionnaire was able to detect improvements in CPET-VO2peak (area under the curve, AUC = 0.77), when using a cut-off value of 1.0 mL·kg− 1·min− 1, while VSAQ (AUC = 0.66) and DASI (AUC = 0.64) could not. Conclusion The self-reported FitMáx©-questionnaire has sufficient validity to estimate aerobic capacity in cancer survivors at group level. The responsiveness of the FitMáx©-questionnaire for absolute change is limited, but the questionnaire is able to detect whether aerobic capacity improved. The FitMáx©-questionnaire showed substantial better values of validity and responsiveness compared to DASI and VSAQ.