Blood Pressure and Brachial Shear Patterns During Recovery from Exercise versus Passive Heat Stress

Cardiovascular disease is the leading cause of mortality in the United States. It is believed that the post‐exercise hypotension (PEH) observed after exercise is an important contributor to the cardioprotective effects of exercise. Additionally, changes in arterial shear stress during exercise are a potent stimulus to vascular adaptation. Recent research has shown similar favorable hemodynamic responses to lower limb hot water immersion (HWI) as during dynamic exercise. It is currently unknown if the post‐HWI hemodynamic responses are similar to those observed after dynamic exercise. Purpose The purpose of this study was to compare the post‐exercise and post‐HWI hemodynamic responses. We hypothesized that young healthy adults would display similar blood pressures and shear‐pattern responses during 60 minutes of recovery from HWI and exercise. Methods Seven young healthy (18–25; 4 female) individuals completed one‐hour of HWI and one‐hour of exercise on separate days, and the responses during recovery were assessed. Subjects were immersed to the level of the sternum in 40°C water during HWI and exercised on a cycle ergometer at 60% of VO 2peak during the exercise intervention. Immediately after each intervention, subjects recovered in the supine position for 60 minutes. At baseline (pre‐intervention) and every 5 minutes throughout recovery, blood pressure (Oscillometric method) was assessed, and brachial artery blood flow (ultrasonography) was assessed at baseline and every 20 minutes during recovery. Mean arterial pressure (MAP) was calculated as 1/3 systolic blood pressure (SBP) + 2/3 diastolic blood pressure (DBP). Paired and unpaired t‐tests were used when appropriate. Results Baseline MAP was similar between interventions at baseline (EX: 86 ± 1.5mmHg vs. HT: 85 ± 2mmHg, p= 0.93). MAP at 20, 40 and 60 minutes post intervention were similar between interventions (EX: 80 ± 4mmHg vs. HT: 78 ± 3mmHg (p=0.26); EX: 77 ± 4mmHg vs. HT: 78 ± 3 mmHg (p= 0.44); EX: 78 ± 3mmHg vs. HT: 79 ± 3mmHg (p=0.39)), but were all significantly reduced relative to baseline values following each intervention (all p<0.05). Likewise, SBP and DBP at 20, 40, and 60 minutes in both interventions were all significantly lower than baseline (all p<0.05), but were not different between interventions. Baseline brachial artery antegrade and retrograde shear were similar between interventions at baseline (antegrade, EX: 190 ± 34 1/s vs. HT: 140 ± 28 1/s (p= 0.63); retrograde, EX: −17 ± 5 1/s vs. HT: −18 ± 5 1/s (p=0.70)). At 20, 40, and 60 minutes post exercise or hot tub, antegrade shear rate was significantly elevated relative to baseline values (all p<0.05), but was not different between interventions. Similarly, in both interventions, there was less retrograde shear rate at all time points relative to baseline, (all p<0.05), but there were no differences between interventions. Conclusion These data suggest that one hour of HWI resulted in post‐intervention blood pressures and brachial blood flow shear responses that were similar to those observed following dynamic exercise. Support or Funding Information HL144128 and Cameron Colbert VPRI Undergraduate Fellowship ‐ University of Oregon This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .