We tested the hypothesis that the work of the heart was not a limiting factor in the attainment of maximal oxygen uptake (VO2 max). We measured cardiac output (Q) and blood pressures (BP) during exercise at two different rates of maximal work to estimate the work of the heart through calculation of the rate-pressure product, as a part of the ongoing discussion regarding factors limiting VO2 max...

BACKGROUND Participation in aerobic exercise generates increased cardiorespiratory fitness, which results in a protective factor for cardiovascular disease and all-cause mortality. High-intensity interval training might cause higher increases in cardiorespiratory fitness in comparison with moderate-intensity continuous training; nevertheless, current evidence is not conclusive. To our knowledge...

OBJECTIVE To evaluate heart rate variability during an inspiratory muscle endurance protocol at three different load levels [30%, 60% and 80% of maximal inspiratory pressure], in patients who had previously undergone coronary artery bypass grafting. METHODS Nineteen late postoperative myocardial revascularization patients participating in a cardiovascular rehabilitation program were studied. ...

Studies in anesthetized rats have implicated GABAA receptors in the region of the medullary raphe pallidus (RP) at the level of the facial nucleus in sympathetic nervous regulation of both heart rate and thermoregulatory mechanisms. Therefore, we examined the effect of microinjection of muscimol, a GABAA receptor agonist, and of bicuculline methiodide (BMI), a GABAA receptor antagonist, into th...

BACKGROUND The relative contributions of decreases in maximal heart rate, stroke volume, and oxygen extraction and of changes in body weight and composition to the age-related decline in maximal oxygen uptake (VO2max) are unclear and may be influenced by sex and level of physical activity. METHODS AND RESULTS To investigate mechanisms by which aging, sex, and physical activity influence VO2ma...