Heat Therapy During Reduced Physical Activity

NCT07847424 | Recruiting

• 1 other identifier: HT-RPA-001
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 1

Brief Summary

The purpose of this randomized controlled trial is to determine whether daily Finnish dry sauna therapy attenuates the adverse cardiovascular, muscular, and metabolic effects of seven days of experimentally reduced physical activity in healthy adults. Participants will be randomized to one of three groups: (1) maintained habitual physical activity with daily sauna therapy, (2) reduced physical activity with daily room-temperature sauna visits (control), or (3) reduced physical activity with daily sauna therapy. Reduced physical activity will be achieved by decreasing daily step count to approximately 1,000 steps per day with the assistance of a power wheelchair. Outcome measures include vascular endothelial function, exercise tolerance, muscle protein synthesis, body composition, blood pressure, glucose regulation, and physiological responses to heat exposure. The study will determine whether passive heat therapy can serve as a practical intervention to preserve cardiometabolic health during short periods of reduced mobility.

Conditions

Physical Inactivity; Vascular Dysfunction; Skeletal Muscle Atrophy

Keywords

Heat Therapy; Physical Inactivity; Sauna; Disuse; Protein Synthesis; Vascular Health

Outcome Measures

Primary Outcomes (4)

• Femoral artery endothelial function

  Common femoral artery blood flow will be measured using Doppler ultrasound at rest and during passive movement of the lower leg through approximately 90 degrees of motion. The hyperemic response may be expressed as peak blood flow, change from resting blood flow, and/or blood-flow area under the curve. The change from baseline to post-intervention will be compared among groups.

  This outcome will be assessed four days prior to the start of the intervention (Day -4) and again 1 day following the final sauna visit (Day 8)

• Change in Maximum Knee-Extension Cycling Power

  Maximum exercise power will be determined during a graded knee-extension cycling test in which resistance is progressively increased until the participant can no longer maintain the required cadence. Maximum power will be reported in watts.

  This outcome will be assessed four days prior to the start of the intervention (Day -4) and again 1 day following the final sauna visit (Day 8)

• Change in Whole-Body Lean Mass

  Whole-body lean mass will be measured using dual-energy X-ray absorptiometry. Lean mass will be reported in kilograms, and the change from baseline to post-intervention will be compared among groups.

  This outcome will be assessed four days prior to the start of the intervention (Day -4) and again 1 day following the final sauna visit (Day 8)

• Integrated Skeletal Muscle Protein Synthesis Rate

  The integrated fractional synthesis rate of skeletal muscle protein will be determined using deuterium oxide labeling and vastus lateralis muscle biopsies. Deuterium incorporation into newly synthesized muscle protein will be quantified by mass spectrometry and expressed as the fractional synthesis rate over the study period, such as percentage per day. Rates will be compared among the three intervention groups.

  Baseline (Day -4) and Day 8

Secondary Outcomes (4)

• Change in Leg Lean Mass

  This outcome will be assessed four days prior to the start of the intervention (Day -4) and again 1 day following the final sauna visit (Day 8)

• Change in Mean Interstitial Glucose Concentration

  Days -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8

• Mean Daily Step Count During the Intervention

  Days -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8

• Change in Core Temperature During Sauna Exposure

  Day 1 and Day 8

Study Arms (3)

Habitual Physical Activity + Sauna

EXPERIMENTAL

Participants will maintain their habitual level of physical activity for seven consecutive days while undergoing one supervised Finnish dry sauna session each day. Sauna treatments will consist of standard Finnish dry sauna exposure according to the study protocol. Participants will undergo comprehensive cardiovascular, muscular, metabolic, and physiological assessments before and after the intervention.

Device: Sauna

Reduced Physical Activity + Room-Temperature Sauna (Control)

SHAM COMPARATOR

Participants will reduce daily physical activity to approximately 1,000 steps per day for seven consecutive days with assistance from a power wheelchair. Participants will attend daily room-temperature sauna sessions that replicate the timing and environment of the sauna intervention without therapeutic heat exposure. Comprehensive outcome assessments will be completed before and after the intervention.

Behavioral: Reduced Physical Activity

Reduced Physical Activity + Dry Sauna

EXPERIMENTAL

Participants will reduce daily physical activity to approximately 1,000 steps per day for seven consecutive days with assistance from a power wheelchair while also completing one supervised Finnish dry sauna session each day. Outcome measures will be assessed before and after the intervention to determine whether heat therapy attenuates the adverse physiological effects of reduced physical activity.

Device: Sauna; Behavioral: Reduced Physical Activity

Interventions

Sauna DEVICE

Participants will complete one supervised dry sauna session each day for seven consecutive days. Sauna exposure will be delivered according to the study protocol using a standard Finnish dry sauna.

Habitual Physical Activity + Sauna; Reduced Physical Activity + Dry Sauna

Reduced Physical Activity BEHAVIORAL

Participants will reduce daily step count to approximately 1,000 steps per day for seven consecutive days. A power wheelchair will be used to assist participants in minimizing ambulation while maintaining normal daily activities.

Reduced Physical Activity + Dry Sauna; Reduced Physical Activity + Room-Temperature Sauna (Control)

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Adults aged 18 years or older
• Healthy men and premenopausal women
• Able and willing to provide written informed consent
• Able to perform knee-extension cycling exercise
• Stable habitual physical activity for at least 3 months before enrollment
• Pass the American College of Sports Medicine (ACSM) Preparticipation Health Screening
• Not currently taking medications known to affect cardiovascular function (e.g., antihypertensive medications or beta-blockers)
• No regular sauna or hot-tub use (fewer than six exposures during the previous 2 months)
• Willing and able to comply with all study procedures, including temporary reduction of physical activity, daily sauna visits, physiological testing, and follow-up assessments

You may not qualify if:

• Younger than 18 years of age
• Failure to pass the ACSM Preparticipation Health Screening
• Unable or unwilling to perform exercise testing
• Current cigarette or marijuana use
• Pregnant or planning to become pregnant during the study
• History or current diagnosis of cardiovascular disease, metabolic disease, or cognitive impairment
• Use of medications known to influence cardiovascular function or exercise tolerance (e.g., antihypertensive medications or beta-blockers)
• Regular sauna or hot-tub use (six or more exposures during the previous 2 months)
• History of heat-related illness
• Any condition that, in the opinion of the investigators, would interfere with safe participation or interpretation of study results
• Inability to understand the study procedures or provide informed consent

Sponsors & Collaborators

• Brigham Young University: lead

Study Sites (1)

Brigham Young University

Provo, Utah, 84602, United States

RECRUITING

MeSH Terms

Conditions

Sedentary Behavior; Muscular Atrophy; Hyperthermia

Interventions

Steam Bath

Condition Hierarchy (Ancestors)

Behavior; Neuromuscular Manifestations; Neurologic Manifestations; Nervous System Diseases; Atrophy; Pathological Conditions, Anatomical; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Body Temperature Changes; Heat Stress Disorders; Wounds and Injuries

Intervention Hierarchy (Ancestors)

Balneology; Therapeutics; Hyperthermia, Induced

Study Officials

• Robert D Hyldahl, PhD

  Brigham Young University

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Robert D Hyldahl, PhD

CONTACT

8014221237; robhyldahl@byu.edu

Jayson R Gifford, PhD

CONTACT

8014223090; jaysongifford@byu.edu

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Masking Details: Due to the nature of the interventions, participants and study personnel administering the interventions will not be masked to group assignment. When feasible, investigators performing outcome analysis will evaluate coded data without knowledge of participant group assignment.
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Associate Professor

Model Details: Participants will be randomly assigned to one of three parallel groups for a 7-day intervention: (1) habitual physical activity with daily Finnish dry sauna therapy, (2) reduced physical activity (\~1,000 steps/day) with daily room-temperature sauna visits (control), or (3) reduced physical activity (\~1,000 steps/day) with daily Finnish dry sauna therapy. All participants will complete identical pre- and post-intervention outcome assessments.

Study Record Dates

• First Submitted: July 14, 2026
• First Posted: September 29, 2026
• Study Start: January 1, 2026
• Primary Completion (Estimated): January 1, 2027
• Study Completion (Estimated): May 1, 2027
• Last Updated: September 29, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)