The study sample consisted of 11 healthy young individuals. All subjects were non-smokers, non-obese and free of any signs or symptoms of disease, as revealed by medical history, physical examination and electrocardiogram at rest and during cardiopulmonary exercise testing. Exclusion criteria were pregnancy, breast-feeding, alcohol or drug abuse, and any medication with potential effects on cardiovascular variables. Subjects were asked not to drink caffeine-containing drinks or exercise for at least 12 and 48 hours, respectively, before the experimental protocols.