Heat Acclimation and ThermotoleranceChronic-XONCT07099872
Chronic Exercise With Overdressing
A study testing Overdressing in people with Heat Acclimation and Thermotolerance, run by United States Army Research Institute of Environmental Medicine at 1 site in United States.
Trial summary
The purpose of this study is to determine if five training sessions of exercise with overdressing can induce heat acclimation. 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?
- Overdressing
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 13 participants
- Where
- 1 siteUnited States
- Study dates
- 28 Oct 2024to 5 May 2025
- 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 45 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Females must be premenopausal.
- Body mass index 18.5-33.0 kg m-2.
- 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 capable of running 2 miles in under 17:00 (8:30 minute mile pace).
- Willing to abstain from exercise and alcoholic beverages for 24 hrs before each study visit.
- Willing to abstain from caffeine for 12 hrs prior to all study visits.
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- Willing to abstain from food for 2 hrs prior to all study visits.
- Willing to abstain from nicotine/tobacco for at least 8 hrs 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.
- Taking dietary supplements, prescriptions, or over the counter medication, other than a contraceptive (unless approved by OMSO \& PI).
- 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).
- Any history of pulmonary, cardiovascular, or renal disease (unless approved by OMSO \& PI).
- Uncontrolled asthma.
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- Current or recent respiratory tract or sinus infections (< 2 weeks prior).
- 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
1 site in 1 country.
United States1 site
US Army Research Institute of Environmental Medicine
Natick, Massachusetts, 01760
About this study
Official title: Efficacy of a Novel Exercise + Overdressing Protocol to Induce Heat Acclimation in Temperate Environments (Chronic XO-Study)
The purpose of this study is to determine if five training sessions of exercise with overdressing can induce heat acclimation.
Read the detailed description
Twelve healthy and fit adults will complete 90 min of exercise (6.0 mph run for 30 min followed by 3.5 mph walk for 60 min) on five occasions at room temperature (~20 °C, 50% RH, 1 mph air velocity). Participants will be randomized into either the exercise with overdressing or exercise wearing standard physical training (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). The investigators hypothesize that, compared to 5 days of exercise in PT clothing, 5 days of exercise with overdressing will lower end-exercise core temperature during standardized HSTs.
- Conditions
- Heat Acclimation and Thermotolerance
- Being tested
- Control, Overdressing
- Keywords
- Heat Acclimation, Heat Stress Test
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
ControlOther
Wear normal attire (shorts/t-shirt) during exercise sessions in a gym-like environment.
OverdressingOther
Wear standardized overdressing ensemble during exercise sessions in a gym-like environment.
| Study group | Role | What they receive |
|---|---|---|
| Exercise with Overdressing | Experimental | 5 days of standardized exercise with overdressing Receives: Other: Overdressing |
| Exercise | Active comparator | 5 days of standardized exercise wearing PT clothing Receives: Other: Control |
What is being measured
The primary outcome is the main question the study is designed to answer.
End-exercise Core Temperature
End-exercise core temperature during heat stress test
Measured: Through study completion, an average of 8 weeks
Resting Core Temperature
Core Temperature at Rest during Heat Stress Test
Measured: Through study completion, an average of 8 weeks
End-exercise heart rate
Heart rate at end of heat stress test
Measured: Through study completion, an average of 8 weeks
End-exercise Mean Weighted Skin Temperature
Mean weighted Skin temperature at end of heat stress test
Measured: Through study completion, an average of 8 weeks
Secondary outcomes (1)
Urine Specific Gravity
Urine specific gravity prior to heat stress test
Measured: Through study completion, an average of 8 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted1 Aug 2025
- Study start28 Oct 2024
- Primary completion5 May 2025
- Study completion5 May 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- 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
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 13 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
- NCT07099872
- Sponsor's protocol ID
- 24-26
- Acronym
- Chronic-XO
- Status last verified
- Jul 2025
- First submitted
- 26 Jun 2025
- Last updated
- 1 Aug 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 1 Aug 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Efficacy of a Novel Exercise + Overdressing Protocol to Induce Heat Acclimation in Temperate Environments (Chronic XO-Study)
- ClinicalTrials.gov ID
- NCT07099872
- Acronym / sponsor ID
- Chronic-XO / 24-26
- Conditions
- Heat Acclimation and Thermotolerance
- Keywords
- Heat Acclimation, Heat Stress Test
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 13 participants (actual)
- Lead sponsor
- United States Army Research Institute of Environmental MedicineUS federal agency
- Study start
- 28 Oct 2024 (actual)
- Primary completion
- 5 May 2025 (actual)
- Study completion
- 5 May 2025 (actual)
- First posted
- 1 Aug 2025 (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.
The purpose of this study is to determine if five training sessions of exercise with overdressing can induce heat acclimation.
Detailed description
Twelve healthy and fit adults will complete 90 min of exercise (6.0 mph run for 30 min followed by 3.5 mph walk for 60 min) on five occasions at room temperature (~20 °C, 50% RH, 1 mph air velocity). Participants will be randomized into either the exercise with overdressing or exercise wearing standard physical training (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). The investigators hypothesize that, compared to 5 days of exercise in PT clothing, 5 days of exercise with overdressing will lower end-exercise core temperature during standardized HSTs.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Exercise with Overdressing | Experimental | Other: Overdressing5 days of standardized exercise with overdressing |
| Exercise | Active comparator | Other: Control5 days of standardized exercise wearing PT clothing |
Who may qualify
- Ages
- 18 to 45 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (9 listed)
- Females must be premenopausal.
- Body mass index 18.5-33.0 kg m-2.
- 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 capable of running 2 miles in under 17:00 (8:30 minute mile pace).
- Willing to abstain from exercise and alcoholic beverages for 24 hrs before each study visit.
Key exclusion criteria (12 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.
- Taking dietary supplements, prescriptions, or over the counter medication, other than a contraceptive (unless approved by OMSO \& PI).
- 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).
- Any history of pulmonary, cardiovascular, or renal disease (unless approved by OMSO \& PI).
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 |
|---|---|---|
| ControlWear normal attire (shorts/t-shirt) during exercise sessions in a gym-like environment. | Other | Exercise |
| OverdressingWear standardized overdressing ensemble during exercise sessions in a gym-like environment. | Other | Exercise with Overdressing |
Primary outcome
End-exercise Core Temperature
Time frame: Through study completion, an average of 8 weeks
End-exercise core temperature during heat stress test
Resting Core Temperature
Time frame: Through study completion, an average of 8 weeks
Core Temperature at Rest during Heat Stress Test
End-exercise heart rate
Time frame: Through study completion, an average of 8 weeks
Heart rate at end of heat stress test
End-exercise Mean Weighted Skin Temperature
Time frame: Through study completion, an average of 8 weeks
Mean weighted Skin temperature at end of heat stress test
1 secondary outcome
Urine Specific Gravity
Time frame: Through study completion, an average of 8 weeks
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 1 Aug 2025.
- Individual participant dataSharing planned: No
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 Overdressing in people with Heat Acclimation and Thermotolerance, 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 9 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 1 Aug 2025. 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?
End-exercise Core Temperature (time frame: Through study completion, an average of 8 weeks). 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?
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 1 Aug 2025; AzTrials last refreshed its copy on 27 Oct 2026.