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

May 28, 2026 updated by: Brett Romano Ely, Providence College

Post-exercise Hot Water Immersion to Improve Blood Pressure Control

The goal of this clinical trial is to test whether putting a participant's 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 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

Completed

Conditions

Intervention / 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 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. 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. The researchers 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. The researchers 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. The researchers 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 (Actual)

20

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Rhode Island
      • Providence, Rhode Island, United States, 02918
        • Providence College

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

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

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
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.
Experimental: Exercise + Heat Therapy
This treatment will include exercise (treadmill walking) and hot leg bath.
Behavioral: Exercise
Participants will walk on a treadmill for 30 minutes at 55-60% of heart rate reserve. The treadmill will be set at 2mph and 2% grade, then be adjusted in the first 5 minutes to achieve target heart rate.
Other Names:
  • Treadmill walking
Other: Heat Therapy
Participants will place their legs in a deep leg bath (mid-calf) set to 42C for 45 minutes.
Other Names:
  • hot leg bath
Experimental: Heat Therapy
This treatment will only include the hot leg bath (no exercise).
Other: Heat Therapy
Participants will place their legs in a deep leg bath (mid-calf) set to 42C for 45 minutes.
Other Names:
  • hot leg bath
Active Comparator: Exercise
This treatment will include exercise (treadmill walking) followed by a sham leg bath.
Behavioral: Exercise
Participants will walk on a treadmill for 30 minutes at 55-60% of heart rate reserve. The treadmill will be set at 2mph and 2% grade, then be adjusted in the first 5 minutes to achieve target heart rate.
Other Names:
  • Treadmill walking
Other: Sham leg bath
Participants will place their legs in a deep leg bath (mid-calf) set to 36C for 45 minutes.
Other Names:
  • lukewarm leg bath

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Ambulatory blood pressure
Time Frame: 24 hours post-treatment
Welch-Allyn ambulatory blood pressure monitor placed on the arm after treatment
24 hours post-treatment
Heart Rate Variability
Time Frame: 30-60 min post-treatment
3-lead ECG with paced breathing measured post-treatment
30-60 min post-treatment
Flow-mediated dilation
Time Frame: 30-60 min post-treatment
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

This is where you will find people and organizations involved with this study.

Sponsor

Providence College

Investigators

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

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 1, 2024

Primary Completion (Actual)

April 10, 2026

Study Completion (Actual)

April 30, 2026

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)

June 1, 2026

Last Update Submitted That Met QC Criteria

May 28, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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