Assessing Cardiorespiratory Fitness in Clinical Rehabilitation: Validity of Field Exercise Tests and Patient-Reported Questionnaires

OBJECTIVES: To evaluate criterion and construct validity of field exercise tests and patient-reported questionnaires compared with cardiopulmonary exercise testing (CPET) to estimate cardiorespiratory fitness (CRF) in clinical rehabilitation. DESIGN: Participants were included at the start of a cardiopulmonary or oncologic rehabilitation program. All patients performed a CPET, steep ramp test (SRT), and 6-minute walk test (6-MWT) and completed the Duke activity status index (DASI), veterans-specific activity questionnaire (VSAQ), and FitMáx© questionnaire (FitMáx). Work rate at peak exercise at the SRT (SRT-WRpeak), distance walked at the 6-MWT (6-MWD), and oxygen uptake at peak exercise (VO2peak) estimated by the questionnaires were compared with measured VO2peak during CPET. RESULTS: Sixty-nine patients (57% female) were included, with a median (IQR) age of 58 (46-66) years. Correlations of SRT-WRpeak and 6-MWD with CPET-VO2peak were ?=0.87 (95%-CI 0.78-0.92) and ?=0.40 (95%-CI 0.17-0.58), respectively. Correlations of DASI-VO2peak, VSAQ-VO2peak, and FitMáx-VO2peak with CPET-VO2peak were ?=0.37 (95%-CI 0.13-0.56), ?=0.51 (95%-CI 0.30-0.68), and ?=0.78 (95%-CI 0.65-0.87), respectively. CONCLUSIONS: SRT-WRpeak and FitMáx-VO2peak strongly correlated with CPET-VO2peak, whereas the 6-MWD, DASI-VO2peak and VSAQ-VO2peak showed a moderate correlation. Consequently, the SRT and FitMáx are considered the best alternative exercise test and questionnaire to estimate CRF when CPET is not feasible.