Heat Acclimation and ThermotoleranceNCT07920536
Evaluation of Exercise With Overdressing to Induce Heat Acclimation in an Average Fitness Warfighter
A study testing Exercise + overdressing in people with Heat Acclimation and Thermotolerance, run by United States Army Research Institute of Environmental Medicine.
Trial summary
A randomized, crossover trial examining five days of exercise \& standardized overdressing versus exercise alone. Read more about this study
- Who is it for?
- Ages 18 to 45 yearsHealthy volunteers can take part
- Conditions the study is for
- Heat Acclimation and Thermotolerance
- What is being tested?
- Exercise + overdressing
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 12 participants
- Where
- No sites listed yet
- Study dates
- Nov 2026to Jun 2028
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 45 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Male or female, age 18-45 (17 if active-duty military).
- In good health as determined by the Office of Medical Support \& Oversight (OMSO) General Medical Clearance.
- Performs aerobic exercise at least 2 times per week and 2 mile run time is between 14:30 and 20:00 minutes.
- Willing to abstain from exercise and alcoholic beverages for 24 hours before each study visit.
- Willing to abstain from caffeine for 12 hours prior to all study visits.
- Willing to abstain from food for 2 hours prior to all study visits.
- Have supervisor approval if permanent party military or a federal employee at U.S. Army Natick Soldier System Center.
Who cannot join
- Frequent hot bath or sauna users (e.g., more than three times a week for the past month).
- Females who are pregnant or planning to become pregnant during the study.
- Females who are menopausal or postmenopausal
- Taking dietary supplements, prescriptions, or over the counter medication, other than a contraceptive (unless approved by OMSO \& PI).
- Any nicotine or recreational drug use (unless quit 1 month prior to the start of the study)
- Abnormal blood count during OMSO medical screening (For example: hemoglobin (Hb) outside of the typical normal values reported by LabCorp in accordance with OMSO (Normal [Hb] Males = 12.6-17.7 g/dL; Females = 11.1-15.9 g/dL) or hematocrit (Hct) outside of the normal ranges (Normal Hct Males = 37.5-51.0%; Females = 34.0-46.6%) levels, presence of abnormal blood chemicals (hemoglobin S or sickle cell traits).
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- Any history of pulmonary, cardiovascular, or renal disease (unless approved by OMSO \& PI).
- Uncontrolled asthma.
- Current or recent respiratory tract or sinus infections (< 2 weeks prior).
- Blood donation (i.e., 550 mL whole blood) during the study or 8 weeks before and after the study
- History of heat stroke or orthostatic intolerance.
- Diagnosed and/or treated for fluid/electrolyte imbalance within the last 30 days.
- History of obstructive disease of the gastrointestinal tract including (but not limited to) diverticulosis, diverticulitis and inflammatory bowel disease, peptic ulcer disease, Crohn's disease, ulcerative colitis.
- Scheduled MRI during testing.
- Allergies to adhesives (e.g., medical tape).
Trial locations and contacts
No sites are listed yet. Contact the study team or a site near you to ask about taking part.
About this study
Official title: Efficacy of an Exercise + Overdressing Protocol to Induce Heat Acclimation in Temperate Environments for the Standard Fitness Warfighter
A randomized, crossover trial examining five days of exercise \& standardized overdressing versus exercise alone.
Read the detailed description
The purpose of this study is to determine the efficacy of five training sessions with overdressing + exercise to induce heat acclimation in individuals with standard fitness levels. Fifteen fit (capable of running 2 miles in 17-20 min), healthy adults will complete 90 minutes of exercise (including running at 6.0mph for up to 15 minutes at 0-1% grade, and walking at 3.5mph for up to 75 minutes at grades ranging from 0%-5%) on five occasions at room tempertature (~20°C, ~50% RH, 1 mph air velocity). Participants will be randomized to begin in either the overdressing + exercise or standard PT clothing group and complete the study in a crossover manner. Heat acclimation induction will be assessed using standardized heat stress tests (HSTs) performed before and after five training sessions. After the final HST has occurred, participants will complete a minimum 4-week washout and then return to repeat the identical protocol in the opposite configuration (overdressing vs. PT clothing).
- Conditions
- Heat Acclimation and Thermotolerance
- Being tested
- Exercise + overdressing
- Keywords
- thermoregulation, adaptation
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Exercise + overdressingOther
Standardized exercise with multiple layers of clothing to stimulate heat loss mechanisms and elicit adaptations
| Study group | Role | What they receive |
|---|---|---|
| Exercise first | Experimental | Five days of exercise alone followed by four week washout then exercise + overdressing Receives: Other: Exercise + overdressing |
| Exercise + Overdressing first | Experimental | Exercise + overdressing following by four week washout and exercise alone Receives: Other: Exercise + overdressing |
What is being measured
The primary outcome is the main question the study is designed to answer.
Core temperature change
Change in core temperature following exercise alone and exercise + overdressing
Measured: 7 days
Heart rate change
Change in heart rate following exercise alone and exercise + overdressing
Measured: 7 days
Skin temperature change
Change in skin temperature following exercise alone and exercise + overdressing
Measured: 7 days
Sweating rate change
Change in sweating rate following exercise alone and exercise + overdressing
Measured: 7 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted5 Nov 2026
- Study startNov 2026 (estimated)
- Primary completionApr 2028 (estimated)
- Study completionJun 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for Heat Acclimation and ThermotoleranceStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- Randomized crossover with four week washout period
- Masking
- None (open label)
- Enrolment
- 12 participants (estimated)
Sponsor and investigators
- Lead sponsor
- United States Army Research Institute of Environmental Medicine
- Sponsor type
- US federal agency
- Responsible party
- Principal investigator, Gabrielle Giersch, United States Army Research Institute of Environmental Medicine
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07920536
- Sponsor's protocol ID
- 26-15H
- Status last verified
- Oct 2026
- First submitted
- 30 Oct 2026
- Last updated
- 5 Nov 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: Cannot share military personnel IDP and some proportion of volunteers will be US Servicemembers.
Publications
Greenfield AM, Brazelton SC, Alba BK, Bodurtha PO, Bradbury KE, Caldwell AR, Chapman CL, Charkoudian N, Connor KR, Conz K, Fry BA, Giersch GEW, Gonzalez-Rojas DH, Heikkinen ME, Looney DP, Mayer TA, McCarthy KG, Potter AW, Rioux TP, Salgado RM, Seeley AD, Shaw MA, Xu X, Ryan BJ. Exercise with overdressing for heat acclimation: a multilayered approach using biophysical modeling and two randomized crossover trials. J Appl Physiol (1985). 2025 Oct 1;139(4):889-901. doi: 10.1152/japplphysiol.00624.2025. Epub 2025 Sep 5.
PubMed 40912903
Study at a glance
From the registry record, last updated by the sponsor on 5 Nov 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Efficacy of an Exercise + Overdressing Protocol to Induce Heat Acclimation in Temperate Environments for the Standard Fitness Warfighter
- ClinicalTrials.gov ID
- NCT07920536
- Acronym / sponsor ID
- 26-15H
- Conditions
- Heat Acclimation and Thermotolerance
- Keywords
- thermoregulation, adaptation
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 12 participants (estimated)
- Lead sponsor
- United States Army Research Institute of Environmental MedicineUS federal agency
- Study start
- Nov 2026 (estimated)
- Primary completion
- Apr 2028 (estimated)
- Study completion
- Jun 2028 (estimated)
- First posted
- 5 Nov 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
A randomized, crossover trial examining five days of exercise \& standardized overdressing versus exercise alone.
Detailed description
The purpose of this study is to determine the efficacy of five training sessions with overdressing + exercise to induce heat acclimation in individuals with standard fitness levels. Fifteen fit (capable of running 2 miles in 17-20 min), healthy adults will complete 90 minutes of exercise (including running at 6.0mph for up to 15 minutes at 0-1% grade, and walking at 3.5mph for up to 75 minutes at grades ranging from 0%-5%) on five occasions at room tempertature (~20°C, ~50% RH, 1 mph air velocity). Participants will be randomized to begin in either the overdressing + exercise or standard PT clothing group and complete the study in a crossover manner. Heat acclimation induction will be assessed using standardized heat stress tests (HSTs) performed before and after five training sessions. After the final HST has occurred, participants will complete a minimum 4-week washout and then return to repeat the identical protocol in the opposite configuration (overdressing vs. PT clothing).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- Randomized crossover with four week washout period
| Arm | Type | Receives |
|---|---|---|
| Exercise first | Experimental | Other: Exercise + overdressingFive days of exercise alone followed by four week washout then exercise + overdressing |
| Exercise + Overdressing first | Experimental | Other: Exercise + overdressingExercise + overdressing following by four week washout and exercise alone |
Who may qualify
- Ages
- 18 to 45 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (7 listed)
- Male or female, age 18-45 (17 if active-duty military).
- In good health as determined by the Office of Medical Support \& Oversight (OMSO) General Medical Clearance.
- Performs aerobic exercise at least 2 times per week and 2 mile run time is between 14:30 and 20:00 minutes.
- Willing to abstain from exercise and alcoholic beverages for 24 hours before each study visit.
- Willing to abstain from caffeine for 12 hours prior to all study visits.
Key exclusion criteria (15 listed)
- Frequent hot bath or sauna users (e.g., more than three times a week for the past month).
- Females who are pregnant or planning to become pregnant during the study.
- Females who are menopausal or postmenopausal
- Taking dietary supplements, prescriptions, or over the counter medication, other than a contraceptive (unless approved by OMSO \& PI).
- Any nicotine or recreational drug use (unless quit 1 month prior to the start of the study)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Exercise + overdressingStandardized exercise with multiple layers of clothing to stimulate heat loss mechanisms and elicit adaptations | Other | Exercise + Overdressing first, Exercise first |
Primary outcome
Core temperature change
Time frame: 7 days
Change in core temperature following exercise alone and exercise + overdressing
Heart rate change
Time frame: 7 days
Change in heart rate following exercise alone and exercise + overdressing
Skin temperature change
Time frame: 7 days
Change in skin temperature following exercise alone and exercise + overdressing
Sweating rate change
Time frame: 7 days
Change in sweating rate following exercise alone and exercise + overdressing
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 5 Nov 2026.
- Background: PubMed 40912903Greenfield AM, Brazelton SC, Alba BK, Bodurtha PO, Bradbury KE, Caldwell AR, Chapman CL, Charkoudian N, Connor KR, Conz K, Fry BA, Giersch GEW, Gonzalez-Rojas DH, Heikkinen ME, Looney DP, Mayer TA, McCarthy KG, Potter AW, Rioux TP, Salgado RM, Seeley AD, Shaw MA, Xu X, Ryan BJ. Exercise with overdressing for heat acclimation: a multilayered approach using biophysical modeling and two randomized crossover trials. J Appl Physiol (1985). 2025 Oct 1;139(4):889-901. doi: 10.1152/japplphysiol.00624.2025. Epub 2025 Sep 5.
- Individual participant dataSharing planned: No. Cannot share military personnel IDP and some proportion of volunteers will be US Servicemembers.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Questions about this trial
What is this clinical trial studying?
A study testing Exercise + overdressing in people with Heat Acclimation and Thermotolerance, run by United States Army Research Institute of Environmental Medicine.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 15 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 5 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Gabrielle E Giersch, PhD (508-206-2421, gabrielle.e.giersch.civ@health.mil), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Core temperature change (time frame: 7 days). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07920536, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 5 Nov 2026.