Acute effects of bolus water intake on post-exercise orthostatic hypotension and cardiovascular hemodynamics

Abstract Introduction Water intake is known to be effective to prevent orthostatic hypotension (OH). However, it is unknown whether water intake would be effective in acutely preventing exercise-induced OH. Methods Fourteen adults (men/women:7/7, age: 20±8 years old) were recruited. Each subject underwent two protocols with and without 500ml water intake using a randomized crossover design (Water vs. Control). They underwent 30 minutes of cycle ergometry at the 60-70% predicted VO2 max. The OH and hemodynamics were assessed before and after exercise, and immediately (Water 1) and 20 minutes (Water 2) after the water intake. The OH was evaluated with a one-minute standing test as the criteria of SBP<90mmHg. The cross-spectral analysis for RR and SBP variabilities was used to evaluate the cardiac autonomic activity and baroreflex sensitivity. Results In both protocols, the incidence of OH increased after the exercise. The incidence of OH was lower in Water than in Control at Water 1 (OR: 0.093, 95% CI: 0.015-0.591). HR was lower and SBP was higher in Water than in Control at Water 1 and 2 (P<0.05). High-frequency power of RR variability and transfer function gains in Water were normalized and higher than in Control at Water 1 and 2 (P<0.05). The ratio of low to high-frequency power of RR variability in Water was normalized and lower in Water than in Control at Water 1 (P<0.05). Conclusion Our findings indicate that water intake may acutely prevent exerciseinduced OH, accompanied by normalized cardiac autonomic activity and baroreflex sensitivity.