Body Temperature Changes, Child Development, Heat, Heat Stress, Physiological Stress
Conditions
Keywords
Thermoregulation, Heat loss, Heat tolerance, Heat strain, Physical activity
Brief summary
Little is known about how children and youth regulate body temperature during exercise across different environmental temperatures compared with young adults, including whether differences in whole-body heat exchange contribute to their responses. The goal of this clinical trial is to determine how ambient temperature affects thermoregulation during exercise in boys and girls aged 9-16 years compared with young adult men and women aged 20-25 years. Participants will complete four study visits at ambient temperatures of 22°C (Celsius; 72°F, Fahrenheit), 26°C (79°F), 31°C (88°F), and 36°C (97°F), while exercising at the same moderate-intensity metabolic heat production of 160 W/m² (W = watts, m = meters). During each visit, participants will complete four 15-minute periods of exercise (exercise bouts 1, 2, 3 and 4 respectively) separated by 15-minute rest periods. Testing will be performed in a whole-body air calorimeter, a specialized chamber that precisely measures heat lost through evaporation and dry heat exchange and the amount of heat stored in the body. These measurements, together with core temperature and heart rate, will allow researchers to determine how increasing ambient temperature affects the body's ability to lose heat and whether these responses differ between children and youth and young adults.
Interventions
OTHERExercise at 22°C
Participants complete intermittent exercise at a metabolic heat production of 160 W/m² in an ambient temperature of 22°C (72°F).
OTHERExercise at 26°C
Participants complete intermittent exercise at a metabolic heat production of 160 W/m² in an ambient temperature of 26°C (79°F).
OTHERExercise at 31°C
Participants complete intermittent exercise at a metabolic heat production of 160 W/m² in an ambient temperature of 31°C (88°F).
OTHERExercise at 36°C
Participants complete intermittent exercise at a metabolic heat production of 160 W/m² in an ambient temperature of 36°C (97°F).
Sponsors
University of Ottawa
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
9 Years to 25 Years
Healthy volunteers
Yes
Inclusion criteria
* Healthy male or female. * Aged 9-16 years or 20-25 years. * Habitually active, defined as participating in regular physical activity at least 3 times per week for at least 20 minutes per session over the previous 6 months. * Able to understand and communicate in English or French. * For participants younger than 18 years, written parental or guardian consent and participant assent are required.
Exclusion criteria
* Acute illness at the time of testing (e.g., cold, flu, or infection). * History of a chronic medical condition that may affect thermoregulation, cardiovascular function, or exercise capacity (e.g., cardiovascular disease, metabolic disorders, respiratory disease including asthma requiring regular medication, or neurological disorders). * Use of medications known to affect thermoregulation, hydration status, or cardiovascular responses. * History of heat-related illness (e.g., heat exhaustion or heat stroke). * Digestive abnormalities or gastrointestinal conditions that may contraindicate ingestion of a telemetry pill. * Any condition that, in the opinion of the investigators, would compromise participant safety or the integrity of the data.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Core temperature | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Core temperature indexed by visceral (telemetry pill) temperature |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Evaporative heat loss | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Evaporative heat loss as assessed using a direct air calorimeter |
| Dry heat loss | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Dry heat loss as assessed using a direct air calorimeter |
| Whole-body total heat loss | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Total heat loss (evaporative + dry) as assessed using a direct air calorimeter |
| Body heat storage | Change from start to end of exercise for each of the four 15 minutes exercise bouts | Heat stored in the body for each of the exercise bouts |
| Skin temperature | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Skin temperature measured at 8-sites (forehead, chest, scapula, upper arm, forearm, hand, thigh, calf) with mean value calculated as weighted values of 8 sites - forehead 7%, chest 17.5%, scapula 17.5%, upper arm 7%, forearm 7%, hand 5%, thigh 19%, and calf 20%. |
| Change in skin temperature | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Skin temperature measured at 8-sites (forehead, chest, scapula, upper arm, forearm, hand, thigh, calf) with mean value calculated as weighted values of 8 sites - forehead 7%, chest 17.5%, scapula 17.5%, upper arm 7%, forearm 7%, hand 5%, thigh 19%, and calf 20%. |
| Heart rate | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Heart rate measured continuously with chest-band telemetric device |
| Thermal sensation | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Thermal sensation will be assessed using the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 7-point scale ("0=neutral to 7=extremely hot") |
Countries
Canada
Contacts
CONTACTGlen P Kenny, PhD
Outcome results
None listed