Cardiovascular responses to head-out water immersion in Korean women breath-hold divers

Head-out water immersion (HOI) increases cardiac output (CO) for a given oxygen consumption. To investigate whether professional breath-hold divers show a similar response, cardiovascular responses to HOI were compared between six Korean women breathhold divers, six non-diving housewives and six non-diving young women at rest and while performing leg cycle exercise of moderate intensity (Deltametabolic rate = similar to100 W m(-2)) in water at a thermoneutral temperature (34.5degreesC). In all three groups, HOI increased CO markedly due to a rise in stroke volume, with no significant change in heart rate (HR) and arterial blood pressure (BP). Thus, total peripheral resistance (TPR) and arterio-venous oxygen content difference fell significantly. During dynamic exercise in water CO increased mainly due to a rise in HR. The arterial systolic BP rose slightly with no significant change in diastolic BP, and the TPR fell 20-40% with similar responses among the three groups of subjects. This study showed that both at rest and during exercise, cardiovascular responses to immersion do not vary significantly with age and water immersion experience.