HOT WATER IMMERSION VERSUS AEROBIC EXERCISE IN LOWERING BLOOD PRESSURE IN ADULTS WITH UNTREATED HYPERTENSION

B.W. Kaiser, C.L. Chapman, E.A. Larson, B.M. Gibson, E.L. Reed, J.R. Halliwill FACSM, C.T. Minson FACSM University of Oregon, Eugene, OR While aerobic exercise training is the current gold-standard non-pharmacological intervention for lowering blood pressure, passive heat therapy has proven to be an effective alternative means of reducing blood pressure. However, efficacy of heat therapy versus exercise training in lowering blood pressure has not been compared in adults with untreated hypertension. PURPOSE: To compare the effectiveness of hot water immersion (HWI) versus aerobic exercise training (EX) in lowering blood pressure in adults with untreated hypertension. METHODS: Six volunteers (age [mean±SD]: 45±10 years, 1F) completed resting vascular function testing, including measurements of blood pressure, cardiac output, and carotid-femoral pulse wave velocity (PWV). Systemic vascular conductance (SVC) was calculated as cardiac output/mean arterial pressure (MAP). Following pre-testing (PRE), subjects were randomized into either HWI (n=4, 1F) or EX (n=2). During HWI, subjects were immersed to the level of the sternum in 40.5°C water for 45 minutes. EX consisted of upright cycling at 60% of heart rate reserve (HRR) for 40 min, with 5 min each for warm-up and cool-down at 30% of HRR. Participants completed 30 sessions of either HWI or EX over 8-10 weeks followed by post-intervention vascular function testing (POST). Values for each group are reported as means ± SD of the change (∆) from PRE to POST and were compared using an unpaired two sample t-test. RESULTS: Following 30 sessions of either HWI or EX, the change in systolic blood pressure tended to be different between groups (HWI vs. EX; -7±8 vs. +2±1 mmHg; p=0.10), whereas change in diastolic blood pressure (DBP) was divergent but not statistically different between HWI and EX (-3±10 vs. +6±10 mmHg; p=0.40). Accordingly, changes in MAP were divergent between HWI and EX (-5±9 vs. +5±6 mmHg; p=0.24). Changes in cardiac output were similar between HWI and EX (-0.62±0.76 vs. -0.01±1.15 L/min; p=0.59), as were changes in SVC (-5.2±10.4 vs. -2.8±15.0 mL•min-1•mmHg-1; p=0.86). Changes in PWV were similar between HWI and EX (-0.2±0.9 vs. -0.4±0.7 m/s; p=0.79). CONCLUSIONS: These data suggest that hot water immersion may be more effective than aerobic exercise training in lowering blood pressure in adults with untreated hypertension. NIH R01HL14412