Effect of Pre-cooling the Body on Whole-body Heat Exchange in Young Males During Exercise in the Heat
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 入组人数
- 10
- 试验地点
- 1
- 主要终点
- Relative change in core temperature at end of exercise
研究概览
简要总结
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.
研究设计
- 研究类型
- Interventional
- 分配方式
- Randomized
- 干预模型
- Crossover
- 主要目的
- Basic Science
- 盲法
- None
入排标准
- 年龄范围
- 18 Years 至 30 Years（Adult）
- 性别
- Male
- 接受健康志愿者
- 是
入选标准
- •Healthy young males (18-30 years)
- •Non-smoking
- •English or French speaking
- •Ability to provide informed consent
排除标准
- •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
研究组 & 干预措施
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.
干预措施: No Cooling (Other)
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).
干预措施: Pre-Cooling (Other)
结局指标
主要结局
Relative change in core temperature at end of exercise
时间窗: Change over the 60-minute exercise bout
Change in rectal temperature from baseline resting.
Heart rate at end exercise
时间窗: Final 15 minutes of exercise
Heart rate during final 15 minutes of exercise. Rectal temperature is measured continuously throughout the intervention.
Core temperature at end of exercise
时间窗: Final 15 minutes of exercise
Rectal temperature during final 15 minutes of exercise. Rectal temperature is measured continuously throughout the intervention.
Evaporative heat loss at end exercise
时间窗: 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
时间窗: 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
时间窗: 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
时间窗: 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
Mean skin temperature at end of exercise
时间窗: 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
时间窗: 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
时间窗: 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
时间窗: 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
时间窗: 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
时间窗: 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
时间窗: 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)
次要结局
- Heart rate variability at end of exercise(Final 15 minutes of exercise)
研究者
Glen P. Kenny
Professor
University of Ottawa