ThermoregulationNCT06670339
Effect of Pre-cooling on Whole-body Heat Loss During Exercise-heat Stress
A study testing No Cooling and Pre-Cooling in people with Thermoregulation and Cold Exposure, run by University of Ottawa at 1 site in Canada.
Trial summary
Endurance exercise performance declines in hot environments as core body temperature increases. To enhance performance, body pre-cooling strategies, such as cold-water immersion have been employed to lower resting core temperature thereby increasing the body's heat storage capacity. Read more about this study
- Who is it for?
- Ages 18 to 30 years, men onlyHealthy volunteers can take part
- Conditions the study is for
- Thermoregulation, Cold Exposure, Heat Stress
- What is being tested?
- No Cooling and Pre-Cooling
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 10 participants
- Where
- 1 siteCanada
- Study dates
- 24 Oct 2024to 27 Feb 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 30 years
- Men only
- Healthy volunteers accepted
- Adult
Who may be able to join
- Healthy young males (18-30 years)
- Non-smoking
- English or French speaking
- Ability to provide informed consent
Who cannot join
- Presence of chronic diseases (e.g., hypertension, diabetes)
- Acute illness (e.g., flu, COVID-19)
- Physical restriction limiting physical activity
- Use of medication judged by the patient or investigators to make participation in this study inadvisable.
- Sedentary
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Effect of Pre-cooling the Body on Whole-body Heat Exchange in Young Males During Exercise in the Heat
Endurance exercise performance declines in hot environments as core body temperature increases. To enhance performance, body pre-cooling strategies, such as cold-water immersion have been employed to lower resting core temperature thereby increasing the body's heat storage capacity. In turn, the increase in body core temperature associated with exercise in the heat is blunted, allowing the individual to exercise at higher intensity and or for a longer period of time. However, the mechanisms by which pre-cooling impacts heat exchange during exercise remain unclear. While existing research has focused on the performance benefits of pre-cooling the body, relatively little is known about the impacts of pre-cooling on whole-body heat exchange during an exercise-heat stress. Investigators will therefore evaluate whole-body heat exchange (dry ± evaporative heat loss as assessed using a direct air calorimeter) during a prolonged (1-hour) moderate-intensity cycling bout in the heat (wet-bulb globe temperature of 29°C; equivalent to 37.5°C, 35% relative humidity) performed with and without pre-cooling by cool-water (~17°C) immersion.
- Conditions
- Thermoregulation, Cold Exposure, Heat Stress, Exercise
- Being tested
- No Cooling, Pre-Cooling
- Keywords
- Cold Stress, Heat Stress, Heat Dissipation, Physical Activity, Performance, Athletes, Workers
- Medical subject headings
- Heat Stress Disorders, Motor Activity
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
No CoolingOther
Participants will not be pre-cooled prior to completing a 60-minute moderate-intensity exercise bout in the heat.
Pre-CoolingOther
Participants will be immersed in cold (~17°C) water to elicit a decrease in rectal temperature by 0.5°C from baseline values prior to completing a 60-min moderate-intensity exercise bout in the heat.
| Study group | Role | What they receive |
|---|---|---|
| No Cooling | Active comparator | Participants will complete 60 min of continuous semi-recumbent cycling at a fixed metabolic heat load (200 W/m2) in the heat (wet-bulb globe temperature of 29°C; 37.5°C and 35% relative humidity) (Control condition) without pre-cooling. Receives: Other: No Cooling |
| Pre-Cooling | Experimental | Participants will undergo a cold-water immersion (~17°C) to elicit a decrease in rectal temperature by 0.5°C from baseline values. Thereafter, once the target temperature is achieved, participants will complete 60 min of continuous moderate-intensity cycling (200 W/m2) in the heat (wet-bulb globe temperature of 29°C; 37.5°C and 35% relative humidity). Receives: Other: Pre-Cooling |
What is being measured
The primary outcome is the main question the study is designed to answer.
Evaporative heat loss at end exercise
Evaporative heat loss as assessed using a direct air calorimeter
Measured: Final 15 minutes of the 60 minutes exercise bout
Dry heat loss at end exercise
Total dry heat loss as assessed using a direct air calorimeter
Measured: Final 15 minutes of the 60 minutes exercise bout
Total heal loss at end exercise
Net heat loss (dry plus/minus evaporative heat exchange) as assessed using a direct air calorimeter
Measured: Final 15 minutes of the 60 minutes exercise bout
Body heat storage during the 60-minute exercise bout
Change in body heat storage (i.e., amount of heat stored in the body) calculated as the temporal summation of metabolic heat production and total heat loss
Measured: Over the 60 minute exercise bout
Core temperature at end of exercise
Rectal temperature during final 15 minutes of exercise. Rectal temperature is measured continuously throughout the intervention.
Measured: Final 15 minutes of exercise
Relative change in core temperature at end of exercise
Change in rectal temperature from baseline resting.
Measured: Change over the 60-minute exercise bout
Heart rate at end exercise
Heart rate during final 15 minutes of exercise. Rectal temperature is measured continuously throughout the intervention.
Measured: Final 15 minutes of exercise
Mean skin temperature at end of exercise
Skin temperature measured continuously at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - upper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%
Measured: Final 15 minutes of exercise
Relative change in skin temperature at end of exercise
Change in skin temperature from baseline resting as assessed at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - uper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%
Measured: Change over the 60-minute exercise bout
Thermal sensation A at end exercise
Thermal sensation assessed via a self-report questionnaire upon verbal prompting (7-point scale; -3: cold to +3: hot)
Measured: Final 15 minutes of exercise
Thermal sensation B at end exercise
Thermal sensation assessed via a self-report questionnaire upon verbal prompting (7-point scale; 0: neutral to 7: extremely hot)
Measured: Final 15 minutes of exercise
Thermal comfort at end exercise
Thermal comfort assessed via a self-report questionnaire upon verbal prompting (4-point scale; 1: comfortable to 4: very uncomfortable)
Measured: Final 15 minutes of exercise
Thirst sensation at end exercise
Thirst sensation assessed via a self-report questionnaire upon verbal prompting (9-point scale; 1: not thirsty at all to 9: very, very thirsty)
Measured: Final 15 minutes of exercise
Rating of perceived exertion
Perceived exertion assessed via a self-report questionnaire upon verbal prompting (6: no exertion at all to 20: maximal exertion)
Measured: Final 15 minutes of exercise
Secondary outcomes (1)
Heart rate variability at end of exercise
Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains (R-R interval data extracted from the electrocardiogram). Measured continuously using a holter monitor with Zymed placement
Measured: Final 15 minutes of exercise
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted1 Nov 2024
- Study start24 Oct 2024
- Primary completion27 Feb 2025
- Study completion27 Feb 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for ThermoregulationStudies 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
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 10 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Ottawa
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Glen P. Kenny, University of Ottawa
- Investigators
- Glen P Kenny, PhD, Principal investigator, University of Ottawa
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06670339
- Sponsor's protocol ID
- HEPRU-2024-08-B
- Status last verified
- Jun 2025
- First submitted
- 28 Oct 2024
- Last updated
- 17 Jun 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Deidentified participant data will be made available with approved analysis plan and signed access agreement
Study at a glance
From the registry record, last updated by the sponsor on 17 Jun 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effect of Pre-cooling the Body on Whole-body Heat Exchange in Young Males During Exercise in the Heat
- ClinicalTrials.gov ID
- NCT06670339
- Acronym / sponsor ID
- HEPRU-2024-08-B
- Conditions
- Thermoregulation, Cold Exposure, Heat Stress, Exercise
- Keywords
- Cold Stress, Heat Stress, Heat Dissipation, Physical Activity, Performance, Athletes, Workers
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 10 participants (actual)
- Lead sponsor
- University of OttawaUniversity, hospital or other
- Study start
- 24 Oct 2024 (actual)
- Primary completion
- 27 Feb 2025 (actual)
- Study completion
- 27 Feb 2025 (actual)
- First posted
- 1 Nov 2024 (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.
Endurance exercise performance declines in hot environments as core body temperature increases. To enhance performance, body pre-cooling strategies, such as cold-water immersion have been employed to lower resting core temperature thereby increasing the body's heat storage capacity. In turn, the increase in body core temperature associated with exercise in the heat is blunted, allowing the individual to exercise at higher intensity and or for a longer period of time. However, the mechanisms by which pre-cooling impacts heat exchange during exercise remain unclear. While existing research has focused on the performance benefits of pre-cooling the body, relatively little is known about the impacts of pre-cooling on whole-body heat exchange during an exercise-heat stress. Investigators will therefore evaluate whole-body heat exchange (dry ± evaporative heat loss as assessed using a direct air calorimeter) during a prolonged (1-hour) moderate-intensity cycling bout in the heat (wet-bulb globe temperature of 29°C; equivalent to 37.5°C, 35% relative humidity) performed with and without pre-cooling by cool-water (~17°C) immersion.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| No Cooling | Active comparator | Other: No CoolingParticipants will complete 60 min of continuous semi-recumbent cycling at a fixed metabolic heat load (200 W/m2) in the heat (wet-bulb globe temperature of 29°C; 37.5°C and 35% relative humidity) (Control condition) without pre-cooling. |
| Pre-Cooling | Experimental | Other: Pre-CoolingParticipants will undergo a cold-water immersion (~17°C) to elicit a decrease in rectal temperature by 0.5°C from baseline values. Thereafter, once the target temperature is achieved, participants will complete 60 min of continuous moderate-intensity cycling (200 W/m2) in the heat (wet-bulb globe temperature of 29°C; 37.5°C and 35% relative humidity). |
Who may qualify
- Ages
- 18 to 30 years
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Healthy young males (18-30 years)
- Non-smoking
- English or French speaking
- Ability to provide informed consent
Key exclusion criteria (5 listed)
- Presence of chronic diseases (e.g., hypertension, diabetes)
- Acute illness (e.g., flu, COVID-19)
- Physical restriction limiting physical activity
- Use of medication judged by the patient or investigators to make participation in this study inadvisable.
- Sedentary
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 |
|---|---|---|
| No CoolingParticipants will not be pre-cooled prior to completing a 60-minute moderate-intensity exercise bout in the heat. | Other | No Cooling |
| Pre-CoolingParticipants will be immersed in cold (~17°C) water to elicit a decrease in rectal temperature by 0.5°C from baseline values prior to completing a 60-min moderate-intensity exercise bout in the heat. | Other | Pre-Cooling |
Primary outcome
Evaporative heat loss at end exercise
Time frame: Final 15 minutes of the 60 minutes exercise bout
Evaporative heat loss as assessed using a direct air calorimeter
Dry heat loss at end exercise
Time frame: Final 15 minutes of the 60 minutes exercise bout
Total dry heat loss as assessed using a direct air calorimeter
Total heal loss at end exercise
Time frame: Final 15 minutes of the 60 minutes exercise bout
Net heat loss (dry plus/minus evaporative heat exchange) as assessed using a direct air calorimeter
Body heat storage during the 60-minute exercise bout
Time frame: Over the 60 minute exercise bout
Change in body heat storage (i.e., amount of heat stored in the body) calculated as the temporal summation of metabolic heat production and total heat loss
Core temperature at end of exercise
Time frame: Final 15 minutes of exercise
Rectal temperature during final 15 minutes of exercise. Rectal temperature is measured continuously throughout the intervention.
Relative change in core temperature at end of exercise
Time frame: Change over the 60-minute exercise bout
Change in rectal temperature from baseline resting.
Heart rate at end exercise
Time frame: Final 15 minutes of exercise
Heart rate during final 15 minutes of exercise. Rectal temperature is measured continuously throughout the intervention.
Mean skin temperature at end of exercise
Time frame: Final 15 minutes of exercise
Skin temperature measured continuously at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - upper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%
Relative change in skin temperature at end of exercise
Time frame: Change over the 60-minute exercise bout
Change in skin temperature from baseline resting as assessed at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - uper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%
Thermal sensation A at end exercise
Time frame: Final 15 minutes of exercise
Thermal sensation assessed via a self-report questionnaire upon verbal prompting (7-point scale; -3: cold to +3: hot)
Thermal sensation B at end exercise
Time frame: Final 15 minutes of exercise
Thermal sensation assessed via a self-report questionnaire upon verbal prompting (7-point scale; 0: neutral to 7: extremely hot)
Thermal comfort at end exercise
Time frame: Final 15 minutes of exercise
Thermal comfort assessed via a self-report questionnaire upon verbal prompting (4-point scale; 1: comfortable to 4: very uncomfortable)
Thirst sensation at end exercise
Time frame: Final 15 minutes of exercise
Thirst sensation assessed via a self-report questionnaire upon verbal prompting (9-point scale; 1: not thirsty at all to 9: very, very thirsty)
Rating of perceived exertion
Time frame: Final 15 minutes of exercise
Perceived exertion assessed via a self-report questionnaire upon verbal prompting (6: no exertion at all to 20: maximal exertion)
1 secondary outcome
Heart rate variability at end of exercise
Time frame: Final 15 minutes of exercise
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 17 Jun 2025.
- Individual participant dataSharing planned: Yes. Deidentified participant data will be made available with approved analysis plan and signed access agreement
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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.
Glen P Kenny, PhD principal investigator
University of Ottawa
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing No Cooling and Pre-Cooling in people with Thermoregulation and Cold Exposure, run by University of Ottawa at 1 site in Canada.
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 4 inclusion and 5 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 17 Jun 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 Canada. 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?
Evaporative heat loss at end exercise (time frame: Final 15 minutes of the 60 minutes exercise bout). The study lists 14 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 17 Jun 2025.