The aim of the study was to assess the intra-session reliability of the oxygen consumption, the carbon dioxide production and the expired minute volume during submaximal exercise test on cycle ergometer during repeated measures with the PowerLab/8M (ADInstrument Pty Ltd., Australia). Methods: Eight aerobically trained participants (age 24 ± 3 years) performed the submaximal exercise test on cycle ergometer. The first load was 1.5 W/kg (4 min) the second load 2.5 W/kg (4 min). The participants undertook 3 repetitions with 15 minutes recovery. The oxygen consumption, the carbon dioxide production and the expired minute volume were recorded by PowerLab/8M during the exercise and analysed with LabChart 7 (ADInstrument Pty Ltd., Australia). The average scores over the last minute in both loads were used for the calculations. Intra-class correlation coefficient ICC2.1 (Shrout & Fleiss, 1979) and standard errors of measurement SEM were used to address relative and absolute reliability. Repeated measures ANOVA were used to assess the systematic error between the three measurements. Results: The ICC2.1 for the oxygen consumption was 0.92, for the carbon dioxide production 0.90, for the expired minute volume 0.94 at the first load (1.5 W/kg). The ICC2.1 for the oxygen consumption was 0.98, for the carbon dioxide production 0.98, for the expired minute volume 0.98 at the second load (2.5 W•kg-1). SEM for the oxygen consumption was 0.05 L/min, for the carbon dioxide production 0.05 L/min, for the expired minute volume 1.28 L at the first load (1.5 W/kg). SEM for the oxygen consumption was 0.04 L/min, for the carbon dioxide production 0.04 L/min, for the expired minute volume 1.16 L at the second load (2.5 W/kg). Discussion: The coefficients of reliability ranged between 0.90 and 0.98. The values 0.90 and higher are considered as a good indicator of reliability in sport science literature (Baumgartner et al., 2006). The value of ICC is, however, influenced by the heterogenity of the research sample. The indication of absolute reliability coefficient should be calculated. We choose the SEM which is one of the most used coefficients along with coefficient of variation and limits of agreement. We agree with Eng et al. (2004) who stated similar values of ICC and SEM for VO2 at submaximal load (1.1 ml/min/kg). In conclusion, we found high reliability of ventilatory parameters measurement during submaximal cycle ergometry measured by PowerLab 8/M.
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