Reliability of the VmaxST Portable Metabolic Measurement System

Abstract

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; V˙O_2peak = 40.7 ml/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 (53.6 m/min), 3.0 mph (80.5 m/min), and 4.0 mph (107.3 m/min) and running at 6.0 mph (160.9 m/min). V˙_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 V˙O₂ and V˙_E of 5.2 – 7.6 %, and 0.77 – 0.92, respectively, for all walking and running trials. For V˙CO₂, 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 V˙_E, V˙O₂ and V˙CO₂, 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 V˙O₂ and V˙_E during walking and running eliciting V˙_E and V˙O₂ at least up to ∼ 56 and 2.2 l/min, respectively. The system appears to be less reliable for measuring V˙CO₂.

Key words

indirect calorimetry - physical activity - reproducibility

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