Validity and feasibility of four standardized aerobic fitness tests in patients with depression: A cross-sectional study

The objective of this study was to examine the validity and feasibility of four standardized aerobic fitness tests to either measure $\dot{V}$ O₂peak or to estimate $\dot{V}$ O₂max (e $\dot{V}$ O₂max) in patients with major depression disorder (MDD). To this end, all subjects (n = 43) performed one maximal cardiopulmonary exercise test with gas exchange measurement (CPET) on a bicycle ergometer. Additionally, three submaximal tests (Åstrand-Rhyming bicycle ergometer test [ART], Physical work capacity test [PWC], and 6-min walk test [6MWT]) were performed within two weeks in counterbalanced order. e $\dot{V}$ O₂max from the submaximal tests was compared to the measured $\dot{V}$ O₂peak from CPET using rANOVAs, Bland-Altman plots, and correlation analyses. Feasibility outcomes (e.g., perceived exertion, discomfort, pretest anxiety, etc.) were compared via rANOVAs. On group level, e $\dot{V}$ O₂max estimated submaximally via ART and PWC did not differ from the CPET-based $\dot{V}$ O₂peak, whereas there was a bias in the 6MWT, as differences of the means increased in participants with higher $\dot{V}$ O₂peak. During CPET, only 56% achieved a primary or secondary criterion of maximum (physiological) exertion. On the group level, $\dot{V}$ O₂peak and e $\dot{V}$ O₂max determined with the different tests showed a sufficient degree of agreement (r ≥ 0.54, ICCs≥0.66, p < 0.001), but on the individual level, marked differences occurred between CPET-based $\dot{V}$ O₂peak and e $\dot{V}$ O₂max. Three of four CRF tests (CPET, ART, PWC) proved to be feasible and could be integrated into everyday therapy and monitoring of patients with MDD as an estimate for improvement of aerobic fitness. For the exact measurement of $\dot{V}$ O₂peak, CPET remains the gold standard, also in patients with MDD.