Post-exercise Hot Water Immersion to Improve Overnight Blood Pressure

NCT ID: NCT06348225

Last Updated: 2025-08-11

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: NA
• Total Enrollment: 20 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-07-01
• Study Completion Date: 2025-12-31

Brief Summary

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.

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.

Conditions

Elevated Blood Pressure

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: PREVENTION
• Blinding Strategy: SINGLE

Study Groups

Exercise + Heat Therapy

This treatment will include exercise (treadmill walking) and hot leg bath.

Group Type: EXPERIMENTAL

Exercise

Intervention Type: BEHAVIORAL

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.

Heat Therapy

Intervention Type: OTHER

Participants will place their legs in a deep leg bath (mid-calf) set to 42C for 45 minutes.

Heat Therapy

This treatment will only include the hot leg bath (no exercise).

Group Type: EXPERIMENTAL

Heat Therapy

Intervention Type: OTHER

Participants will place their legs in a deep leg bath (mid-calf) set to 42C for 45 minutes.

Exercise

This treatment will include exercise (treadmill walking) followed by a sham leg bath.

Group Type: ACTIVE_COMPARATOR

Exercise

Intervention Type: BEHAVIORAL

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.

Sham leg bath

Intervention Type: OTHER

Participants will place their legs in a deep leg bath (mid-calf) set to 36C for 45 minutes.

Control

Participants will refrain from exercise or heat exposure for at least 24 hours, and perform all study analyses for a control comparison.

Group Type: NO_INTERVENTION

No interventions assigned to this group

Interventions

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.

Intervention Type: BEHAVIORAL

Heat Therapy

Participants will place their legs in a deep leg bath (mid-calf) set to 42C for 45 minutes.

Intervention Type: OTHER

Sham leg bath

Participants will place their legs in a deep leg bath (mid-calf) set to 36C for 45 minutes.

Intervention Type: OTHER

Other Intervention Names

Treadmill walking; hot leg bath; lukewarm leg bath

Eligibility Criteria

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

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 50 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Providence College

OTHER

Sponsor Role: lead

Responsible Party

Brett Romano Ely

Assistant Professor of Health Sciences

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Brett R Ely, PhD

Role: PRINCIPAL_INVESTIGATOR

Providence College

Locations

Providence College

Providence, Rhode Island, United States

Site Status: RECRUITING

Countries

United States

Central Contacts

Kris A Monahan, PhD

Role: CONTACT

kmonaha6@providence.edu

401.865.2554

Dalila G Alves

Role: CONTACT

dalves@providence.edu

401.865.2935

Facility Contacts

Brett R Ely, PhD

Role: primary

bely@providence.edu

401-865-2632

Provided Documents

Document Type: Study Protocol and Statistical Analysis Plan

View Document

Document Type: Informed Consent Form

View Document

Other Identifiers

FY24-10

Identifier Type: -

Identifier Source: org_study_id