Post-exercise Hot Water Immersion to Improve Overnight Blood Pressure (ExHT)

Post-exercise Hot Water Immersion to Improve Blood Pressure Control

The goal of this clinical trial is to test whether putting your legs in a hot bath after exercise improves blood pressure in people with higher blood pressure.

. The main questions it aims to answer are:

• Whether exercise alone, hot water leg bath alone, or both treatments together cause blood pressure to be lower during sleep.
• If there are any changes in heart rhythm or blood vessel health after exercise, hot water leg bath, or the two treatments together that relate to changes in blood pressure.

Participants will complete four different trials:

• 30 minutes of walking with a 45-minute lukewarm leg bath after
• 30 minutes of walking with a 45-minute hot leg bath after
• 45 minutes of a hot leg bath with no exercise
• A day with no exercise or leg bath Researchers will look at their heart rhythm, blood vessels, and blood pressure after each of these trials to see if there are differences, and if exercise and heat together can improve heart health more than exercise or heat alone.

Study Overview

• Status: Not yet recruiting
• Conditions: Elevated Blood Pressure
• Intervention / Treatment: Other: Exercise or heat treatment

Detailed Description

In 2017, the American Heart Association updated standards for diagnosing hypertension, while emphasizing the need for lifestyle modification in the early stages of blood pressure elevation. Using these updated criteria, approximately 1/3 of U.S. adults have hypertension, but few are able to improve their blood pressure through diet and exercise and often progress to more severe disease states. Novel interventions to promote blood pressure reduction in mild hypertension are needed to attenuate or prevent this progression to more severe hypertension. Heat therapy, the repeated application of passive heat through hot water immersion, has gained recent attention for promising blood pressure reduction and improvement in cardiovascular health. Our preliminary work combining exercise and hot water leg immersion indicates improved overnight blood pressure in individuals with elevated blood pressure, but the magnitude and mechanisms of this improvement require further study.

It is unknown whether the decrease in blood pressure following post-exercise heat exposure results from changes in systemic regulation (autonomic nervous system function, measured through heart rate variability), local factors (improved blood vessel function, measured through flow-mediated dilation), or both. The goal of the proposed research is to examine the impact of exercise alone (30 minutes of treadmill walking), hot water immersion alone (45 minutes in a leg bath set to 42°C), and combined exercise + hot water immersion (30 minutes treadmill walking followed by 45 minutes in a 42°C leg bath) on nocturnal blood pressure, autonomic function, and blood vessel function in individuals with elevated blood pressure. This goal will be addressed with the following specific aims:

Aim 1. To examine the impact of exercise, hot water leg immersion, or combined exercise + hot water immersion on overnight blood pressure in individuals with elevated blood pressure. We hypothesize that the combination of exercise and hot water immersion will result in reduced systolic and diastolic blood pressure through 12 hours post-exercise as compared to baseline or either standalone treatment.

Aim 2. To examine changes in autonomic function, as measured by heart rate variability (HRV) following exercise, leg heating, or combined therapies. We hypothesize that combined exercise and hot water immersion will result in higher HRV (indicating improved autonomic balance) compared to baseline measures.

Aim 3. To examine changes in blood vessel (endothelial) function, measured using flow-mediated dilation, following exercise, leg heating, or combined therapies. We hypothesize that combined exercise and hot water immersion will result in a higher flow-mediated dilation (indicating improved blood vessel relaxation) compared to baseline or either standalone intervention.

The results of this study have important health implications in the treatment of hypertension using lifestyle interventions for the millions of Americans with elevated blood pressure or hypertension. The findings have the potential to improve non-pharmacological treatment of hypertension by developing an exercise and heat exposure protocol that is cost-effective, easily implemented, and results in substantially reduced blood pressure and improved cardiovascular risk profile.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Kris A Monahan, PhD; Phone Number: 401.865.2554; Email: kmonaha6@providence.edu
• Study Contact Backup: Name: Dalila G Alves; Phone Number: 401.865.2935; Email: dalves@providence.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• resting blood pressure >120/80 mmHg; measured at screening visit
• BMI between 18-39.9
• capable of walking 30 min at a moderate intensity on a treadmill

Exclusion Criteria:

• diagnosed hypertension
• taking antihypertensive medications
• history of heat injury or heat illness

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Exercise + Heat Therapy; 30 minutes treadmill walking at a speed and grade to elicit 55-60% of heart rate reserve, followed by 45 minutes with the legs immersed to mid-calf in water circulating at 42C	Other: Exercise or heat treatment; Interventions will be each of the four arms described previously, administered ~1 week apart in a randomized, counter-balanced fashion.
Experimental: Heat Therapy; 45 minutes with the legs immersed to mid-calf in water circulating at 42C	Other: Exercise or heat treatment; Interventions will be each of the four arms described previously, administered ~1 week apart in a randomized, counter-balanced fashion.
Active Comparator: Exercise; 30 minutes treadmill walking at a speed and grade to elicit 55-60% of heart rate reserve (matched between Exercise + Heat Therapy and Exercise days), followed by 45 minutes with the legs immersed to mid-calf in water circulating at 36C	Other: Exercise or heat treatment; Interventions will be each of the four arms described previously, administered ~1 week apart in a randomized, counter-balanced fashion.
No Intervention: Control; Participants will refrain from exercise or heat exposure for at least 24 hours, and perform all study analyses for a control comparison.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Ambulatory blood pressure	Welch-Allyn ambulatory blood pressure monitor placed on the arm after treatment	24 hours post-treatment
Heart Rate Variability	3-lead ECG with paced breathing measured post-treatment	30-60 min post-treatment
Flow-mediated dilation	Measure of endothelial function in the brachial artery (arm), change in blood vessel diameter following a 5-minute blood flow occlusion and release	30-60 min post-treatment

Collaborators and Investigators

• Sponsor: Providence College
• Investigators: Principal Investigator: Brett R Ely, PhD, Providence College

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2024
• Primary Completion (Estimated): December 31, 2025
• Study Completion (Estimated): December 31, 2025

Study Registration Dates

• First Submitted: March 28, 2024
• First Submitted That Met QC Criteria: March 28, 2024
• First Posted (Actual): April 4, 2024

Study Record Updates

• Last Update Posted (Actual): April 4, 2024
• Last Update Submitted That Met QC Criteria: March 28, 2024
• Last Verified: March 1, 2024

More Information

Terms related to this study

• Keywords: exercise, heat therapy
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Vascular Diseases; Hypertension
• Other Study ID Numbers: FY24-10

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: The current plan is to share only compiled data with other researchers if requested.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No