Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
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.
Not provided
Not provided
Not provided
Not provided
Not provided
| Label | Type | Description | Intervention Names |
|---|---|---|---|
| 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. |
|
| 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). |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| No Cooling | Other | Participants will not be pre-cooled prior to completing a 60-minute moderate-intensity exercise bout in the heat. |
|
| Measure | Description | Time Frame |
|---|---|---|
| Evaporative heat loss at end exercise | Evaporative heat loss as assessed using a direct air calorimeter | 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 | 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 | 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 | 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. | Final 15 minutes of exercise |
| Relative change in core temperature at end of exercise | Change in rectal temperature from baseline resting. | 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. |
| Measure | Description | Time Frame |
|---|---|---|
| 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 | Final 15 minutes of exercise |
Not provided
Inclusion Criteria:
Exclusion Criteria:
Not provided
Not provided
Not provided
Not provided
Not provided
| Name | Affiliation | Role |
|---|---|---|
| Glen P Kenny, PhD | University of Ottawa | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| University of Ottawa | Ottawa | Ontario | K1N6N5 | Canada |
Deidentified participant data will be made available with approved analysis plan and signed access agreement
Following publication of the main study report(s)
Approved analysis plan and signed access agreement
Not provided
Not provided
| ID | Term |
|---|---|
| D018882 | Heat Stress Disorders |
| D009043 | Motor Activity |
| ID | Term |
|---|---|
| D014947 | Wounds and Injuries |
| D001519 | Behavior |
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
Not provided
| Pre-Cooling | 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. |
|
| 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% | 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% | 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) | 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) | 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) | 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) | 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) | Final 15 minutes of exercise |