The validity of five brands of cycle ergometers was evaluated by the comparison of the Vo₂ requirements at different displayed power.

Five physically active men performed a continuous incremental exercise test on five ergometers (Ergomeca, Lifecycle, Monark, Polar S710 and CompuTrainer). The latter was also compared with a standard dynamometer in order to associate Vo₂ values with the real power. Every test started with a 5-min warm-up on the same cycle ergometer (Ergomeca) at 100 W to make sure that the Vo₂ differences do not come from Vo₂ measurement error. Only last minute steady-state Vo₂ values of each 2-min stage were used for the Vo₂–watt curve. Large differences (5– 10 ml kg^–1 min^–1) at the same displayed power indicate inaccuracy of displayed power output (PO). Using corrected power values from the dynamometer revealed that for the same Vo₂ the CompuTrainer underestimates PO by ~30 W between 100 and 300 W, whereas the Lifecycle overestimate it by 3–53 W from 100 to 300 W. The Monark and Polar S710 underestimate PO by 15 W and the Ergomeca by ~5 W.

Inaccuracies between –10% and 18% in displayed PO of various cycle ergometers question their interchangeability.