Heat Acclimation and ThermotoleranceEXHOTCONNCT07307391
Exercise in Extreme Hot Weather Conditions
A study testing hot wet high (HWH), hot dry high (HDH) and Experimental: hot dry low (HWL) in people with Heat Acclimation and Thermotolerance and Heat Effect, run by University of Valladolid at 1 site in Spain.
Trial summary
Background: Core body temperature increases in hot climates due to exercise workload, disrupting heat gain and loss of balance. The human thermoregulatory system regulates core body temperature through factors such as metabolic heat production, air temperature, humidity, and clothing. Read more about this study
- Who is it for?
- Ages 18 to 50 yearsHealthy volunteers can take part
- Conditions the study is for
- Heat Acclimation and Thermotolerance, Heat Effect
- What is being tested?
- hot wet high (HWH), hot dry high (HDH) and Experimental: hot dry low (HWL)
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 6 participants
- Where
- 1 siteSpain
- Study dates
- 7 Jul 2025to 12 Dec 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 50 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Participation at the regional competition level
- Receiving monetary remuneration for their sports engagement
- Participating in sports activities in the previous six years
- Average training experience of 6.0±1.4 years
- A weekly volume of 6.3±0.7 days for 2.3±0.7 hours (h)·day-¹.
Who cannot join
- A 2 kg weight change in the previous month
- Adherence to special diets
- Use of nutritional supplements
- Smoking
- An acute or chronic communicable or noncommunicable disease
- Heat allergic problems.
Trial locations and contacts
1 site in 1 country.
Spain1 site
Faculty of Health Sciences, University of Valladolid Soria Campus, Soria, Soria 42004
Soria, Soria, 42004
About this study
Official title: Physiological Responses in Semi-professional Athletes: a Comparison of the Effects of Hot Weather Conditions
Background: Core body temperature increases in hot climates due to exercise workload, disrupting heat gain and loss of balance. The human thermoregulatory system regulates core body temperature through factors such as metabolic heat production, air temperature, humidity, and clothing. The study investigates physiological thermoregulatory responses in semiprofessional athletes during walking and jogging in different climatic conditions.
Methods: A factorial experimental interventional design was used to evaluate different physical activity (low (L)=5 km/h and high (H)=8 km/h) and climatic conditions within the Thermal Environment Laboratory at Lund University, Sweden. The temperature within the climatic chamber was set at 40°C and 31°C, with a relative humidity of 20% and 70%, (hot dry (HD) and hot humid (HW), respectively, to account for a 28°C WBGT. The study used independent T-tests, ANOVA and simple linear regression models to analyse the physiological responses of semiprofessional athletes under different test conditions, comparing gender differences.
- Conditions
- Heat Acclimation and Thermotolerance, Heat Effect
- Being tested
- hot wet high (HWH), hot dry high (HDH), Experimental: hot dry low (HWL), Experimental: hot wet low (HWL)
- Keywords
- Heat Stress, Exposure time, Gender difference, WBGT
- 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.
hot wet high (HWH)Other
Air Temperature (ºC) 30.6±1.2 Relative Humidity (%) 68.6±1.3 Vapour Pressure (kPa) 1011±1.1 Bruel and Kjear (WBGT ºC) 27.3±0.8 Heat Stress (WBGT ºC) 27.8±0.8 Air Velocity (m/s) 0.45±0.19
hot dry high (HDH)Other
Relative Humidity (%) 39.7±0.3 Vapor Pressure (kPa) 29.0±1.2 Bruel and Kjear (WBGT ºC) 1007.9± 6.4 Heat Stress (WBGT ºC) 28.9±0.6 Air Velocity (m/s) 28.4±0.3
Experimental: hot dry low (HWL)Other
Relative Humidity (%) 31.1±0.1 Vapor Pressure (kPa )67.1±1.0 Bruel and Kjear (WBGT ºC)1005.7±8.0 Heat Stress (WBGT ºC) 27.4±0.6 Air Velocity (m/s) 27.9±0.3
Experimental: hot wet low (HWL)Other
Relative Humidity (%) 39.8±0.1 Vapor Pressure (kPa) 26.4±0.4 Bruel and Kjear (WBGT ºC) 1004.7±10.7 Heat Stress (WBGT ºC) 28.3±0.3 Air Velocity (m/s) 27.7±0.1
| Study group | Role | What they receive |
|---|---|---|
| hot wet high (HWH) | Experimental | Air Temperature (ºC) 30.6±1.2 Relative Humidity (%) 68.6±1.3 Vapour Pressure (kPa) 1011±1.1 Bruel and Kjear (WBGT ºC) 27.3±0.8 Heat Stress (WBGT ºC) 27.8±0.8 Air Velocity (m/s) 0.45±0.19 Receives: Other: hot wet high (HWH) |
| hot dry high (HDH) | Experimental | Relative Humidity (%) 39.7±0.3 Vapor Pressure (kPa) 29.0±1.2 Bruel and Kjear (WBGT ºC) 1007.9± 6.4 Heat Stress (WBGT ºC) 28.9±0.6 Air Velocity (m/s) 28.4±0.3 Receives: Other: hot dry high (HDH) |
| hot dry low (HWL) | Experimental | Relative Humidity (%) 31.1±0.1 Vapor Pressure (kPa )67.1±1.0 Bruel and Kjear (WBGT ºC)1005.7±8.0 Heat Stress (WBGT ºC) 27.4±0.6 Air Velocity (m/s) 27.9±0.3 Receives: Other: Experimental: hot dry low (HWL) |
| hot wet low (HWL) | Experimental | Relative Humidity (%) 39.8±0.1 Vapor Pressure (kPa) 26.4±0.4 Bruel and Kjear (WBGT ºC) 1004.7±10.7 Heat Stress (WBGT ºC) 28.3±0.3 Air Velocity (m/s) 27.7±0.1 Receives: Other: Experimental: hot wet low (HWL) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Exposure Time
duration an athlete is exposed to a specific intensity or environmental condition
Measured: Just one day, the day of the test, in those weather conditions
Heart Rate
measures how hard your heart works to gauge fitness
Measured: Just one day, the day of the test, in those weather conditions
Oxygen Uptake
how much oxygen your body uses during activity
Measured: Just one day, the day of the test, in those weather conditions
Secondary outcomes (6)
Core Body Temperature
the body's internal temperature regulation
Measured: Just one day, the day of the test, in those weather conditions
Skin Temperature
The temperature of your body's surface
Measured: Just one day, the day of the test, in those weather conditions
Body Temperature
the internal heat level of the human body
Measured: Just one day, the day of the test, in those weather conditions
Sweat Rate
the amount of fluid your body loses through sweat per hour during exercise
Measured: Just one day, the day of the test, in those weather conditions
Perceived Exertion Level
is a subjective scale that measures how hard your body feels it's working during exercise
Measured: Just one day, the day of the test, in those weather conditions
Thermal Sensation Level
The Thermal Sensation Level is a standardized, subjective rating system used to quantify a person's perception of warmth or coolness in their environment
Measured: Just one day, the day of the test, in those weather conditions
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted29 Dec 2025
- Study start7 Jul 2025
- Primary completion10 Dec 2025
- Study completion12 Dec 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
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- A factorial experimental interventional study design
- Masking
- None (open label)
- Enrolment
- 6 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Valladolid
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Diego Fernández Lázaro, University of Valladolid
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07307391
- Sponsor's protocol ID
- 2025.14.11
- Acronym
- EXHOTCON
- Status last verified
- Dec 2025
- First submitted
- 14 Dec 2025
- Last updated
- 31 Dec 2025
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 31 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Physiological Responses in Semi-professional Athletes: a Comparison of the Effects of Hot Weather Conditions
- ClinicalTrials.gov ID
- NCT07307391
- Acronym / sponsor ID
- EXHOTCON / 2025.14.11
- Conditions
- Heat Acclimation and Thermotolerance, Heat Effect
- Keywords
- Heat Stress, Exposure time, Gender difference, WBGT
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 6 participants (actual)
- Lead sponsor
- University of ValladolidUniversity, hospital or other
- Study start
- 7 Jul 2025 (actual)
- Primary completion
- 10 Dec 2025 (actual)
- Study completion
- 12 Dec 2025 (actual)
- First posted
- 29 Dec 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.
Background: Core body temperature increases in hot climates due to exercise workload, disrupting heat gain and loss of balance. The human thermoregulatory system regulates core body temperature through factors such as metabolic heat production, air temperature, humidity, and clothing. The study investigates physiological thermoregulatory responses in semiprofessional athletes during walking and jogging in different climatic conditions.
Methods: A factorial experimental interventional design was used to evaluate different physical activity (low (L)=5 km/h and high (H)=8 km/h) and climatic conditions within the Thermal Environment Laboratory at Lund University, Sweden. The temperature within the climatic chamber was set at 40°C and 31°C, with a relative humidity of 20% and 70%, (hot dry (HD) and hot humid (HW), respectively, to account for a 28°C WBGT. The study used independent T-tests, ANOVA and simple linear regression models to analyse the physiological responses of semiprofessional athletes under different test conditions, comparing gender differences.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 4
- Model description
- A factorial experimental interventional study design
| Arm | Type | Receives |
|---|---|---|
| hot wet high (HWH) | Experimental | Other: hot wet high (HWH)Air Temperature (ºC) 30.6±1.2 Relative Humidity (%) 68.6±1.3 Vapour Pressure (kPa) 1011±1.1 Bruel and Kjear (WBGT ºC) 27.3±0.8 Heat Stress (WBGT ºC) 27.8±0.8 Air Velocity (m/s) 0.45±0.19 |
| hot dry high (HDH) | Experimental | Other: hot dry high (HDH)Relative Humidity (%) 39.7±0.3 Vapor Pressure (kPa) 29.0±1.2 Bruel and Kjear (WBGT ºC) 1007.9± 6.4 Heat Stress (WBGT ºC) 28.9±0.6 Air Velocity (m/s) 28.4±0.3 |
| hot dry low (HWL) | Experimental | Other: Experimental: hot dry low (HWL)Relative Humidity (%) 31.1±0.1 Vapor Pressure (kPa )67.1±1.0 Bruel and Kjear (WBGT ºC)1005.7±8.0 Heat Stress (WBGT ºC) 27.4±0.6 Air Velocity (m/s) 27.9±0.3 |
| hot wet low (HWL) | Experimental | Other: Experimental: hot wet low (HWL)Relative Humidity (%) 39.8±0.1 Vapor Pressure (kPa) 26.4±0.4 Bruel and Kjear (WBGT ºC) 1004.7±10.7 Heat Stress (WBGT ºC) 28.3±0.3 Air Velocity (m/s) 27.7±0.1 |
Who may qualify
- Ages
- 18 to 50 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (5 listed)
- Participation at the regional competition level
- Receiving monetary remuneration for their sports engagement
- Participating in sports activities in the previous six years
- Average training experience of 6.0±1.4 years
- A weekly volume of 6.3±0.7 days for 2.3±0.7 hours (h)·day-¹.
Key exclusion criteria (6 listed)
- A 2 kg weight change in the previous month
- Adherence to special diets
- Use of nutritional supplements
- Smoking
- An acute or chronic communicable or noncommunicable disease
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 |
|---|---|---|
| hot wet high (HWH)Air Temperature (ºC) 30.6±1.2 Relative Humidity (%) 68.6±1.3 Vapour Pressure (kPa) 1011±1.1 Bruel and Kjear (WBGT ºC) 27.3±0.8 Heat Stress (WBGT ºC) 27.8±0.8 Air Velocity (m/s) 0.45±0.19 | Other | hot wet high (HWH) |
| hot dry high (HDH)Relative Humidity (%) 39.7±0.3 Vapor Pressure (kPa) 29.0±1.2 Bruel and Kjear (WBGT ºC) 1007.9± 6.4 Heat Stress (WBGT ºC) 28.9±0.6 Air Velocity (m/s) 28.4±0.3 | Other | hot dry high (HDH) |
| Experimental: hot dry low (HWL)Relative Humidity (%) 31.1±0.1 Vapor Pressure (kPa )67.1±1.0 Bruel and Kjear (WBGT ºC)1005.7±8.0 Heat Stress (WBGT ºC) 27.4±0.6 Air Velocity (m/s) 27.9±0.3 | Other | hot dry low (HWL) |
| Experimental: hot wet low (HWL)Relative Humidity (%) 39.8±0.1 Vapor Pressure (kPa) 26.4±0.4 Bruel and Kjear (WBGT ºC) 1004.7±10.7 Heat Stress (WBGT ºC) 28.3±0.3 Air Velocity (m/s) 27.7±0.1 | Other | hot wet low (HWL) |
Primary outcome
Exposure Time
Time frame: Just one day, the day of the test, in those weather conditions
duration an athlete is exposed to a specific intensity or environmental condition
Heart Rate
Time frame: Just one day, the day of the test, in those weather conditions
measures how hard your heart works to gauge fitness
Oxygen Uptake
Time frame: Just one day, the day of the test, in those weather conditions
how much oxygen your body uses during activity
6 secondary outcomes
Core Body Temperature
Time frame: Just one day, the day of the test, in those weather conditions
Skin Temperature
Time frame: Just one day, the day of the test, in those weather conditions
Body Temperature
Time frame: Just one day, the day of the test, in those weather conditions
Sweat Rate
Time frame: Just one day, the day of the test, in those weather conditions
Perceived Exertion Level
Time frame: Just one day, the day of the test, in those weather conditions
Thermal Sensation Level
Time frame: Just one day, the day of the test, in those weather conditions
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 31 Dec 2025.
Related trials for Heat Acclimation and Thermotolerance
Recruiting
Climate-Responsive Nutrition, WASH, and Heat Counselling for Maternal and Child Health in Sindh, Pakistan
Maternal Nutrition, Child Nutrition
Recruiting
Structural Heat Adaptation and Education in Urban Setting
Heat Illness, Quality of Life
Recruiting
Assessing the Effectiveness of Heat Adaptation Digital Messages From Primary Care Providers to Their Patients on the Change in Behaviour for Heatwave-related Preparedness
Heathly Subjects, Primary Health Care
Recruiting
Heat Adaptation Through Community-based Approaches and Research at SEACO: Structural and Behavioural Interventions (Heat Care)
Climate Change, Heat; Weather
Recruiting
Structural Heat Adaptation and Education in Rural Setting
Heat Illness, Quality of Life
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 hot wet high (HWH), hot dry high (HDH) and Experimental: hot dry low (HWL) in people with Heat Acclimation and Thermotolerance and Heat Effect, run by University of Valladolid at 1 site in Spain.
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 5 inclusion and 6 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 31 Dec 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 Spain. 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?
Exposure Time (time frame: Just one day, the day of the test, in those weather conditions). The study lists 3 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 31 Dec 2025.