Vasodilatation in the muscle microcircle was evaluated using VO₂on kinetics in constant load cycle ergometer exercise, at load less of 10% than that corresponding to anaerobic threshold in previous incremental test identified. At onset of this constant load exercise, VO₂ increases early and fast [first phase (φI)]; it follows a slower increase [second phase (φII)], which appears with variable delay, and reaches in about 3 minutes steady-state [third phase (φIII)] by single exponential function. We excluded φI from our measurements because invalided by many fakes. ΨII was attributed to O₂ decreased content in active muscles blood, where this undergoes a gas exchange. ΨII time constant (τ) can be decreased by exercise training so as heart disease therapy, whereas heart diseases prolong τ owing to inadequate vasodilatation in muscle microcirculation due especially to NO defect and circulating vasoconstrictors increase. Therefore, τ can be considered an indirect endothelial function and dysfunction marker. We tested, by original method, healthy subjects and patients with ischemic-hypertensive cardiopathy, IIa and IIb NYHA class, in treatment according to ESC-ESH guidelines, and subjects with cardiovascular (CV) risk factors and CV damage present, mild or absent, assessing drugs effects, as β1 blockers, doxazosin and tadalafil, on endothelial function, and as a guide to therapy CV in order to normalise or significantly improve τ and therefore endothelial function.