The Impact of Acute Hot or Cold Water Immersion on Post‐Exercise Blood Pressure Regulation

Abstract

Acute exercise, heat exposure, and cold exposure independently produce short‐term changes in blood pressure (BP). It is currently unknown whether post‐exercise hot water immersion (HWI) or cold water immersion (CWI) impact the magnitude or timeline of changes in BP observed following exercise. The objective of this study was to examine the impact of post‐exercise HWI and CWI on systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP). Ten healthy (6M, 4F; BMI: 23.7±1.7; BP: 125±3/73±3 mmHg) individuals took part in 3 randomized, counterbalanced trials consisting of evening interval exercise (~7k treadmill walking and running with 8×400m high‐intensity intervals) followed by a 30 minute treatment of HWI (immersed to chest in 39–40°C tub), CWI (immersed to chest in 14–15°C tub) or time control (CON; seated passive recovery at room temperature). Brachial BP was measured in triplicate in a seated position pre‐exercise (Pre‐Ex), immediately post‐exercise (Post‐Ex), immediately post‐treatment (Post‐Tx), and following 12h overnight recovery (12h post). Results were analyzed using a 2‐way repeated measures ANOVA. Significant time by treatment interactions were observed for DBP (p=0.0070) and MAP (p=0.0059). Pre‐Ex and Post‐Ex, no differences were observed between groups. Post‐Tx, CWI resulted in increased DBP (+12 ± 3 mmHg; p<0.0001) and MAP (+9 ± 2 mmHg; p=0.0002) compared with Pre‐Ex, while DBP and MAP remained steady in HWI and CON. 12‐hr post‐exercise, both MAP (−6 ± 2mmHg; p=0.0431) and DBP (−7 ± 2mmHg; p=0.0159) were lower than Pre‐Ex in HWI, and no differences were seen in CWI or CON. These data indicate that post‐exercise CWI temporarily increases DBP and MAP, but does not affect blood pressure 12‐h post‐exercise. In contrast, post‐exercise HWI leads to prolonged reductions in DBP and MAP in healthy individuals. Those engaging in exercise to control or reduce blood pressure may experience a greater benefit with the addition of post‐exercise HWI. Future research should examine whether this effect is similarly observed in hypertensive individuals, as first‐morning blood pressure is an important indicator of disease severity and progression.