Cardiac output with modified cardio-impedance against inert gas rebreathing during sub-maximal and maximal cycling exercise in healthy and fit subjects.

[Formula: see text] seems to represent a valuable alternative to invasive methods for assessing [Formula: see text] during sub-maximal exercise. The [Formula: see text] underestimation with respect to [Formula: see text] during supra-maximal exercise suggests that [Formula: see text] might be less optimal for supra-maximal intensities.