Effect of Pre-cooling on Whole-body Heat Loss During Exercise-heat Stress

NCT ID: NCT06670339

Last Updated: 2025-06-17

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 10 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-10-24
• Study Completion Date: 2025-02-27

Brief 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. 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

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: NONE

Study Groups

No Cooling

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.

Group Type: ACTIVE_COMPARATOR

No Cooling

Intervention Type: OTHER

Participants will not be pre-cooled prior to completing a 60-minute moderate-intensity exercise bout in the heat.

Pre-Cooling

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).

Group Type: EXPERIMENTAL

Pre-Cooling

Intervention Type: OTHER

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.

Interventions

No Cooling

Participants will not be pre-cooled prior to completing a 60-minute moderate-intensity exercise bout in the heat.

Intervention Type: OTHER

Pre-Cooling

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.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Healthy young males (18-30 years)
• Non-smoking
• English or French speaking
• Ability to provide informed consent

Exclusion Criteria

• 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

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 30 Years
• Eligible Sex: MALE
• Accepts Healthy Volunteers: Yes

Sponsors

University of Ottawa

OTHER

Sponsor Role: lead

Responsible Party

Glen P. Kenny

Professor

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Glen P Kenny, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Ottawa

Locations

University of Ottawa

Ottawa, Ontario, Canada

Countries

Canada

Other Identifiers

HEPRU-2024-08-B

Identifier Type: -

Identifier Source: org_study_id