This study investigated how cardiovascular responses affect tissue oxygenation at rest and during exercises in water. Nine healthy men performed cycling exercises on land (LE) and in water (WE) at xiphoid levels of 40 and 60% V02 ,peak. The V02, heart rate (HR), cardiac output (CO), total peripheral resistance (TPR) and mean blood pressure (MBP) were measured. The oxy-haemogbloin (Hb02) and total-haemoglobin (THb) were also measured using near infrared spectroscopy (NIRS). At rest, the CO and stroke volume (SV) increased (p<0.05) with immersion. A correlative increase in the Hb02 level was noted. These results indicate that the oxygen supply to the muscles increased on immersion. Contrarily, the MBP during WE was higher (p<0.05) than that of LE at both intensities. The Hb02level during WE was lower than that of LE at both intensities The water pressure seems to restrict the blood flow, thereby increasing MBP through activation of a muscle metaboreceptor or mechanoreceptor.
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