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

Water intake is known to be effective in preventing orthostatic hypotension (OH). However, it is unknown whether water intake would be effective in acutely preventing exercise-induced OH.

Fourteen adults (men/women: 7/7, age: 20 ± 8 years) were recruited. Each subject underwent two protocols with and without 500 ml water intake using a randomized crossover design (Water vs. Control). Participants underwent 30 min of cycle ergometry at the 60-70% predicted VO₂ max. OH and hemodynamics were assessed before and after exercise, and immediately (Water 1) and 20 min (Water 2) after the water intake. OH was evaluated with a 1-min standing test as the criteria for systolic blood pressure (SBP) < 90 mmHg. A cross-spectral analysis for RR and SBP variability was used to evaluate the cardiac autonomic activity and baroreflex sensitivity.

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). Heart rate 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).

Our findings indicate that water intake may prevent acute exercise-induced OH, accompanied by normalized cardiac autonomic activity and baroreflex sensitivity.