Cardiac output and heart rate in man during simulated swimming while breath-holding

We measured stroke volume (SV), heart rate (HR), cardiac output (Q), arterial pressure and intrapulmonic (mouth) pressure in four healthy, male subjects during simulated swimming (i.e., performing crawl movements with the legs continuously at a constant rhythm) with and without apnea (water temperature: 31°C). We wanted to see whether the exercise tachycardia response persisted, or wheter the HR decreased during apnea, just as in the «diving response» of diving animals