Reliability of the VmaxST portable metabolic measurement system

The purpose of this study was to evaluate the reliability of the VmaxST portable metabolic measurement system. Forty-five healthy adults (age=25.7 ± 5.9 yr; height=171.8 ± 9.1 cm; weight =69.6 ± 12.8 kg; V̇O_2peak=40.7ml/kg/min; percent fat=21.7 ± 11.0) performed two separate and identical exercise routines on different days consisting of treadmill walking at 2.0 mph (53.6m/min), 3.0 mph (80.5m/min), and 4.0 mph (107.3 m/min) and running at 6.0 mph (160.9m/min). V̇_E and gas exchange were measured continuously breath-to-breath. A random effects model on log-transformed data yielded coefficients of variation (CV) and intraclass correlation coefficients (ICC) for V̇O₂ and V̇_E of 5.2-7.6%, and 0.77-0.92, respectively, for all walking and running trials. For V̇C_O2, CVs were higher (10-12%) and ICCs lower (0.70-0.81). Ordinary least squares regression between the individual difference scores and the individual mean scores for V̇_E, V̇O₂ and V̇C_O2, respectively, indicated no systematic bias (all p > 0.05). Bland-Altman analysis also illustrated no systematic bias between repeated measurements. The VmaxST provides reliable measurements of V̇O ₂ and V̇_E during walking and running eliciting V̇_E and V̇O₂ at least up to ∼ 56 and 2.2 l/min, respectively. The system appears to be less reliable for measuring V̇CO₂.