Heat Stress, ExertionalNCT05292170
Influences of Female Sex and Reproductive Hormones on Physiological Aspects of Heat Acclimation
A study testing Heat acclimation in people with Heat Stress, Exertional, run by United States Army Research Institute of Environmental Medicine at 1 site in United States.
Trial summary
Women are often understudied in thermal physiology research, leaving recommendations for Soldier safety and performance in hot conditions based largely on data collected in men. Female sex hormones estradiol and progesterone clearly have non-reproductive physiological effects, including influences on thermoregulatory… Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Heat Stress, Exertional
- What is being tested?
- Heat acclimation
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 27 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Oct 2021to 30 Apr 2024
- Phase
- Interventional
- Are there results?
- None posted in the registry
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 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- • Males and females, age 18-40 y (17 y for active duty military)
- Eumenorrheic females (menstrual cycle length between 24-35 days) or females taking oral contraceptives
- In good health as determined by OMSO (Office of Medical Support and Oversight) General Medical Clearance and willing to report all medications and dietary supplements (i.e. cold medication, Tylenol. Aleve) to the PI and OMSO.
- Passed his/her most recent Army Combat Fitness Test (ACFT) (military volunteers only) or exercise at least 2 times per week (civilian volunteers)
- Willing to not exercise, or drink alcoholic beverages for 24 hours before each testing session
- Willing to not consume caffeine 12 hours prior to any testing sessions
- Willing to refrain from additional moderate to strenuous physical activity throughout testing period
- Males and females with BMI <30
Who cannot join
- • Females who are pregnant or planning to become pregnant during the study
- Females utilizing implantable contraception (intrauterine device, implantable bar)
- Tested positive for COVID-19 within the past 30 days.
- Taking prescription or over the counter medication, other than a contraceptive (unless approved by OMSO and Principal Investigator (PI))
- Tobacco users, or anyone who has used tobacco within the last four months
- Physical problems/injuries that would affect walking or running on a treadmill
Show all 12Show fewer
- Allergy to skin adhesive
- Heart, lung, kidney, muscle, endocrine, or nerve disorder(s)
- History of heat intolerance 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
Trial locations and contacts
1 site in 1 country.
United States1 site
U.S. Army Research Institute of Environmental Medicine
Natick, Massachusetts, 01760
About this study
Women are often understudied in thermal physiology research, leaving recommendations for Soldier safety and performance in hot conditions based largely on data collected in men. Female sex hormones estradiol and progesterone clearly have non-reproductive physiological effects, including influences on thermoregulatory and cardiovascular function. However, mechanisms of differing physiological adaptations to repeated heat exposure (i.e., heat acclimation) as a function of reproductive hormone status have yet to be investigated in a systematic way. Understanding possible sex differences in adaptation or mechanisms for adaptation during heat acclimation is important to ultimately optimize interventions to maximize soldier health and safety during training and deployment in the heat. Our goals in the present study are to evaluate physiological and biophysical responses to a standard heat acclimation protocol in a group of young, healthy men and women. Thirty individuals (n=10 males, n=10 women with a low hormonal status (i.e. early follicular phase), n=10 women with a high hormonal status (i.e. midluteal phase)) will complete 10 consecutive days of exercise (treadmill walking: 3.1 mph/2% grade) in the heat (40°C /40% relative humidity) up to 3hr per day. Changes in core temperature, heart rate, and sex hormones will be assessed to examine differences in thermoregulatory response to heat acclimation.
- Conditions
- Heat Stress, Exertional
- Being tested
- Heat acclimation
- Medical subject headings
- Heat Stress Disorders
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Heat acclimationOther
10 consecutive days of heat acclimation
| Study group | Role | What they receive |
|---|---|---|
| Males | Experimental | 10 consecutive day heat acclimation in males Receives: Other: Heat acclimation |
| Females + high hormones | Experimental | 10 consecutive day heat acclimation in females with high hormonal dose Receives: Other: Heat acclimation |
| Females + low hormones | Experimental | 10 consecutive day heat acclimation in females with low hormonal dose Receives: Other: Heat acclimation |
What is being measured
The primary outcome is the main question the study is designed to answer.
Core temperature
Measured: 10 days
Heart rate
Measured: 10 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Mar 2022
- Study start1 Oct 2021
- Primary completion30 Apr 2024
- Study completion30 Apr 2024
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 Stress, ExertionalStudies 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
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 27 participants (actual)
Sponsor and investigators
- Lead sponsor
- United States Army Research Institute of Environmental Medicine
- Sponsor type
- US federal agency
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05292170
- Sponsor's protocol ID
- 21-07Hc
- Status last verified
- Aug 2024
- First submitted
- 14 Mar 2022
- Last updated
- 7 Aug 2024
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
Brazelton SC, Charkoudian N, Bradbury KE, Salgado RM, Giersch GEW. Inter-individual variability in physiological adaptations during heat acclimation in adults: Contributions of body mass index and body size. Physiol Rep. 2026 Jan;14(2):e70713. doi: 10.14814/phy2.70713.
PubMed 41546148
Study at a glance
From the registry record, last updated by the sponsor on 7 Aug 2024. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Influences of Female Sex and Reproductive Hormones on Physiological Aspects of Heat Acclimation
- ClinicalTrials.gov ID
- NCT05292170
- Acronym / sponsor ID
- 21-07Hc
- Conditions
- Heat Stress, Exertional
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 27 participants (actual)
- Lead sponsor
- United States Army Research Institute of Environmental MedicineUS federal agency
- Study start
- 1 Oct 2021 (actual)
- Primary completion
- 30 Apr 2024 (actual)
- Study completion
- 30 Apr 2024 (actual)
- First posted
- 23 Mar 2022 (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.
Women are often understudied in thermal physiology research, leaving recommendations for Soldier safety and performance in hot conditions based largely on data collected in men. Female sex hormones estradiol and progesterone clearly have non-reproductive physiological effects, including influences on thermoregulatory and cardiovascular function. However, mechanisms of differing physiological adaptations to repeated heat exposure (i.e., heat acclimation) as a function of reproductive hormone status have yet to be investigated in a systematic way. Understanding possible sex differences in adaptation or mechanisms for adaptation during heat acclimation is important to ultimately optimize interventions to maximize soldier health and safety during training and deployment in the heat. Our goals in the present study are to evaluate physiological and biophysical responses to a standard heat acclimation protocol in a group of young, healthy men and women. Thirty individuals (n=10 males, n=10 women with a low hormonal status (i.e. early follicular phase), n=10 women with a high hormonal status (i.e. midluteal phase)) will complete 10 consecutive days of exercise (treadmill walking: 3.1 mph/2% grade) in the heat (40°C /40% relative humidity) up to 3hr per day. Changes in core temperature, heart rate, and sex hormones will be assessed to examine differences in thermoregulatory response to heat acclimation.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Males | Experimental | Other: Heat acclimation10 consecutive day heat acclimation in males |
| Females + high hormones | Experimental | Other: Heat acclimation10 consecutive day heat acclimation in females with high hormonal dose |
| Females + low hormones | Experimental | Other: Heat acclimation10 consecutive day heat acclimation in females with low hormonal dose |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (8 listed)
- • Males and females, age 18-40 y (17 y for active duty military)
Key exclusion criteria (12 listed)
- • Females who are pregnant or planning to become pregnant during 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 |
|---|---|---|
| Heat acclimation10 consecutive days of heat acclimation | Other | Females + high hormones, Females + low hormones, Males |
Primary outcome
Core temperature
Time frame: 10 days
Heart rate
Time frame: 10 days
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 7 Aug 2024.
- Derived from this study: PubMed 41546148Brazelton SC, Charkoudian N, Bradbury KE, Salgado RM, Giersch GEW. Inter-individual variability in physiological adaptations during heat acclimation in adults: Contributions of body mass index and body size. Physiol Rep. 2026 Jan;14(2):e70713. doi: 10.14814/phy2.70713.
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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. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Heat acclimation in people with Heat Stress, Exertional, run by United States Army Research Institute of Environmental Medicine at 1 site in United States.
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 8 inclusion and 12 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: finished, as of the sponsor's last update on 7 Aug 2024. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
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?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Core temperature (time frame: 10 days). The study lists 2 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 NCT05292170, 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 7 Aug 2024.