Effects of water immersion in supine position on arterial stiffness in humans

The purpose of this study was to investigate the effects of characteristics of water (Exp 1), and the effects of water temperature (Exp 2) on arterial stiffness in supine position during human water immersion. Six healthy males (age : 23.3±2.2 years, height : 174.2±8.5 cm, weight : 71.7±7.5kg; mean±SD) participated in the study. Expl ; Subjects maintained supine position for 5 minutes on land (L condition) or in water set the water temperature at 36°C (WT-36 condition). Brachial-ankle Pulse Wave Velocity (baPWV), heart rate and blood pressure were measured in all subjects. There was no significant difference between the L-condition and WT-36 condition in all parameters. These results suggested that other factors have a strong effect toward baPWV as compared with water pressure and buoyancy. Exp 2 ; Subjects maintained supine position for 5 minutes in water set the water temperature at 30, 36 and 40°C (WT-30 condition, WT-36 condition, WT-40 condition respectively). baPWV and diastolic blood pressure at WT-30 condition were significantly higher than those at WT-36 condition and WT-40 condition (ρ<0.05). Heart rate and blood pressure are potentially influential factors on baPWV These findings suggested that baPWV was influenced by cause an increase in peripheral resistance during 30°C condition. In conclusion, it was shown that arterial stiffness was changed influence by water temperature during human water immersion.