Exercise in Extreme Hot Weather Conditions

NCT07307391 | Completed DMC

• 1 other identifier: 2025.14.11
• Study Type: interventional
• Target: 6
• Locations: 1 country
• Sites: 1

Brief 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. 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 Effect; Heat Acclimation and Thermotolerance

Keywords

Heat Stress; Exposure time; Gender difference; WBGT

Outcome Measures

Primary Outcomes (3)

• Exposure Time

  duration an athlete is exposed to a specific intensity or environmental condition

  Just one day, the day of the test, in those weather conditions

• Heart Rate

  measures how hard your heart works to gauge fitness

  Just one day, the day of the test, in those weather conditions

• Oxygen Uptake

  how much oxygen your body uses during activity

  Just one day, the day of the test, in those weather conditions

Secondary Outcomes (6)

• Core Body Temperature

  Just one day, the day of the test, in those weather conditions

• Skin Temperature

  Just one day, the day of the test, in those weather conditions

• Body Temperature

  Just one day, the day of the test, in those weather conditions

• Sweat Rate

  Just one day, the day of the test, in those weather conditions

• Perceived Exertion Level

  Just one day, the day of the test, in those weather conditions

Study Arms (4)

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

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

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

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

Other: Experimental: hot wet low (HWL)

Interventions

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

hot wet low (HWL)

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 wet high (HWH)

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

hot dry high (HDH)

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

hot dry low (HWL)

Eligibility Criteria

• Age: 18 Years - 50 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• University of Valladolid: lead

Study Sites (1)

Faculty of Health Sciences, University of Valladolid Soria Campus, Soria, Soria 42004

Soria, Soria, 42004, Spain

Location

MeSH Terms

Conditions

Heat Stress Disorders

Condition Hierarchy (Ancestors)

Wounds and Injuries

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor Doctor

Model Details: A factorial experimental interventional study design

Study Record Dates

• First Submitted: December 14, 2025
• First Posted: December 29, 2025
• Study Start: July 7, 2025
• Primary Completion: December 10, 2025
• Study Completion: December 12, 2025
• Last Updated: December 31, 2025

Record last verified: 2025-12

Locations

ES (1)