Validity and reliability of the axiom powertrain cycle ergometer when compared with an SRM powermeter

The purpose of this study was to determine the validity and the reliability of a stationary electromagnetically-braked cycle ergometer (Axiom PowerTrain) against the SRM power measuring crankset. Nineteen male competitive cyclists completed four tests on their bicycle equipped with a 20-strain gauges SRM crankset: a maximal aerobic power (MAP) test and three 10-min time trials (TTs) with three different simulated slopes (0, 3, and 6%). The Axiom ergometer overestimated (p < 0.05) the SRM power output during the last stage of the MAP test and during TTs, by 5% and 12%, respectively. Power output (PO) of the Axiom ergometer drifted significantly (p < 0.05) with the time during TT. These findings indicate that the Axiom ergometer does not provide a valid measure of PO compared with SRM. However, the small coefficient of variation (2.2%) during the MAP test indicates that the Axiom provides a reliable PO and that it can be used e.g. for relative PO comparisons with competitive cyclists during a race season.