Body Temperature Changes, Child Development, Heat, Heat Stress, Physiological Stress
Conditions
Keywords
Thermoregulation, Heat loss, Heat strain, Heat tolerance, Exercise-heat stress
Brief summary
Little is known about how children and youth regulate body temperature during exercise in the heat 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 exercise intensity affects thermoregulation in boys and girls aged 9-16 years compared with young adult men and women aged 20-25 years. Participants will complete three study visits in a hot environment of 36°C (degree Celcius (97°F, degree Farenheit)), performing light-, moderate-, and vigorous-intensity exercise corresponding to metabolic heat production of 120, 160, and 200 W/m² (w=watts, m=meter), respectively. During each visit, participants will complete four 15-minute bouts of exercise (i.e., bout 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 exercise intensity affects the body's ability to lose heat and whether these responses differ between children and youth and young adults.
Interventions
OTHERLow-Intensity Exercise in the Heat
Participants complete intermittent low-intensity exercise at a metabolic heat production of 120 W/m² (w=watts; m=meter) in a hot environment of 36°C (degree Celsius (97°F, degree Fahrenheit)).
OTHERModerate-Intensity Exercise in the Heat
Participants complete intermittent moderate-intensity exercise at a metabolic heat production of 160 W/m² in a hot environment of 36°C (97°F).
OTHERVigorous-Intensity Exercise in the Heat
Participants complete intermittent vigorous-intensity exercise at a metabolic heat production of 200 W/m² in a hot environment 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
FEMALE
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 (dry + evaporative) as assessed using a direct air calorimeter |
| Body Heat Storage | Change from start to the end 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 value 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 | Change from start to the end for each of the four 15 minutes exercise bouts | Skin temperature measured at 8-sites (forehead, chest, scapula, upper arm, forearm, hand, thigh, calf) with mean value calculated as weighted value of 8 sites - forehead, 7%; chest, 17.5%; scapula, 17.5%, upper arm, 7%; forearm, 7%; hand, 5%; thigh, 19%; and calf, 20%. |
| Thermal Sensation Scale | 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") |
| Heart rate | End of each of the four 15 minutes exercise bouts (average of last 5 minutes) | Measured continuously with chest-band device |
Countries
Canada
Outcome results
None listed