Postexercise hypotension and heart rate variability response after water- and land-based high-intensity interval...

A randomized crossover trial was carried out in prehypertensive obese men to compare postexercise hypotension and heart rate variability (HRV) following water-based and land-based high-intensity interval exercises (HIIEs). Nine prehypertensive obese participants, aged 23.6± 2.4 years, were randomly assigned to one of three interventions: no-exercise control, HIIE with immersion up to the chest, or HIIE on dry land. In the evenings of three separate days, participants performed either of the interventions. Matched with exercise volume, both HIIEs composed of 5 repetitions of 30-sec sprints at maximum effort followed by a 4-min rest. Ambulatory blood pressure and HRV were measured before the interventions and over the 24-hr following period. Both HIIEs resulted in significant reductions of average 24-hr mean arterial pressure (-6.7 mmHg). Notably, the water-based HIIE resulted in a significantly higher reduction of 24-hr systolic blood pressure (SBP) (-9 mmHg) than the land-based HIIE, particularly at night, in addition to a significantly longer duration of postexercise hypotension. Finally, the water-based HIIE was more effective at restoring HRV during recovery. Our findings demonstrated postexercise hypotension following the HIIEs, particularly the water-based HIIE. During recovery, the water-based HIIE was remarkably effective at restoring HRV. These findings indicate that water-based HIIE is more effective at reducing SBP and requires less recovery time than land-based HIIE in prehypertensive obese men.