The purpose of the present study is to compare the intramuscular oxygen hemodynamics in and out of water in order to investigate the potential value of underwater exercises for elderly patients with hypertension. After the sensor of a laser tissue blood-oxygen monitor was installed over the right vastus medialis muscle of 5 healthy aged subjects and aged hypertension patients who are receiving medical therapy, tissue oxygen saturation (StO₂) level, tissue hemoglobin (HbT) level, tissue deoxygenated hemoglobin (HbD) level, and tissue oxygenated hemoglobin (HbO₂) level were measured. Measurements were made under each of 6 conditions: standing, sitting, lying supine on the ground, standing in water up to the navel or to the xiphoid positions and lying supine on the water. In both healthy subjects and those with hypertension, the heart rate was the highest while standing on the ground, followed by sitting on the ground and lying supine on the ground. It was slightly higher while standing in water up to the navel position than when supine on the ground, and was the lowest while standing in water up to the xiphoid position. In healthy subjects and the hypertension patients, StO₂ level was the lowest while standing on the ground, followed by sitting on the ground and lying supine. It was slightly lower while standing in water up to the navel position than while lying supine on the ground, but was the highest when standing immersed to the xiphoid position. The StO₂ level can be calculated from the ratio of tissue oxygenated hemoglobin level / tissue hemoglobin level. The StO₂ level appeared to increase due to the decrease the tissue hemoglobin level in femoral blood hemodynamics because the changes in posture or water pressure increased the venous return. Decreased heart rate increases the cardiac stroke volume due to increased the venous return, suggesting that both control group and hypertensive patients also show the same reactions.

DESCENTE SPORTS SCIENCE Vol.25/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE