The validity of the VO₂ Master Pro for measuring oxygen consumption during sedentary activity and treadmill walking and jogging

Metabolic carts are commonly used to estimate oxygen consumption (V̇O₂) during exercise, but are largely limited to controlled laboratory settings. The V̇O₂ Master Pro (VMP) is a newer, portable metabolic analyzer designed to address this limitation; however, few studies have evaluated the validity of this device at varying activity levels. This study aimed to assess the validity of the VMP in measuring V̇O₂ compared with a stationary metabolic cart, the COSMED Quark CPET (CQ), during sedentary activity and treadmill walking/jogging in a laboratory setting. Twenty-seven healthy adults (mean age = 22.1 ± 7.6 years; female = 51.8%) participated in two laboratory trials on separate days. In a counterbalanced order, participants used the CQ and VMP during 10 min conditions of the following activities: sedentary activity (sitting quietly), slow walking (3.2 km/h), brisk walking (5.6 km/h), and jogging (7.2 km/h). The agreement between the two measures was evaluated using equivalence testing, mean absolute percentage error (MAPE), percentage bias, intraclass correlation coefficients (ICCs), and Bland-Altman analyses. The devices showed low agreement and significant proportional biases across all activity levels (ICCs = 0.135-0.323). Equivalence testing did not demonstrate statistically significant equivalence between the devices (<i>p</i> > 0.05), with the VMP underestimating V̇O₂. The smallest error appeared during jogging (MAPE = 20.05%; percentage bias= -19.29%). The VMP underestimated V̇O₂ at all tested intensities, demonstrating low accuracy and agreement relative to the reference measure. This may be attributed to limited ventilatory flow capture or sensor responsiveness during submaximal activities. Observed bias and within-subject variability suggest caution when using the VMP across different submaximal activity levels.