Test-retest variability of VO2max using total-capture indirect calorimetry reveals linear relationship of VO 2 and Power.

This study aimed to analyze the intra-individual variation in VO2max of human subjects using total-capture and free-flow indirect calorimetry. Twenty-seven men (27±5 year; VO2max 49-79 ml•kg-1 •min-1 ) performed two maximal exertion tests (CPETs) on a cycle ergometer, separated by a 7±2 day interval. VO2 and VCO2 were assessed using an indirect calorimeter (Omnical) with total capture of exhalation in a free-flow airstream. Thirteen subjects performed a third maximal exertion test using a breath-by-breath calorimeter (Oxycon Pro). On-site validation was deemed a requirement. For the Omnical, the mean within-subject CV for VO2max was 1.2±0.9% (0.0-4.4%) and for ergometer workload Pmax 1.3±1.3% (0-4.6%). VO2max values with the Oxycon Pro were significantly lower in comparison to Omnical (P<0.001; t-test) with mean 3570 versus 4061 and difference SD 361 ml•min-1 . Validation results for the Omnical with methanol combustion were -0.05±0.70% (mean±SD; n=31) at the 225 ml•min-1 VO2 level and -0.23±0.80% (n=31) at the 150 ml•min-1 VCO2 level. Results using gas-infusion were 0.04±0.75% (n=34) and -0.99±1.05% (n=24) over the respective 500-6000 ml•min-1 VO2 and VCO2 ranges. Validation results for the Oxycon pro in breath-by-breath mode were - 2.2±1.6% (n=12) for VO2 and 5.7±3.3% (n=12) for VCO2 over the 1000-4000 ml•min-1 range. On a Visual Analogue Scale participants reported improved breathing using the free-flow (score 7.6±1.2 versus 5.1±2.7, p=0.008). We conclude that total capturing free-flow indirect calorimetry is suitable for measuring VO2 even with the highest range. VO2max was linear with the incline in Pmax over the full range. This article is protected by copyright. All rights reserved.