previous diagnosis of systolic heart failure (left ventricular ejection fraction <40%) under optimized clinical treatment as judged by the accompanying physician.

hospital admission in the previous 6 weeks;

exercise training program in the previous 6 months;

nitrate therapy (e.g., isosorbide dinitrate);

tabagism;

any condition that could interfere with the ability to exercise;

diagnosed psychiatric or cognitive disorders;

type i insulin-dependent diabetes mellitus;

excessively over-weight (bmi>35kg/m²);

other diagnosed cardiorespiratory disorders (e.g., chronic obstructive pulmonary disease, peripheral artery disease).