RecruitingACTRN12622000501741

Is thermoregulatory capacity altered in children during exercise in hot weather?

Is thermoregulatory capacity altered in children? Defining the critical environmental limits for children exercising in heat stress conditions.

Sponsor

The University of Sydney

Enrollment

48 participants

Start Date

May 1, 2022

Study Type

Interventional

Conditions

Summary

Numerous clinical and public health organizations clearly state that children have thermoregulatory impairments that render them more susceptible to heat-related illness. However, other than commenting that children may be at a disadvantage, very few extreme heat policies specifically differentiate between adults and children for the upper environmental limit at which exercise and/or sporting events should be modified or cancelled. The overall aim of the proposed project is to use a novel experimental approach to determine the independent influence of developmental age on the environmental limits (i.e., maximum relative humidity at 35°C) for safe exercise in the heat. The primary research question guiding this project is: Is thermoregulatory strain (and the critical environmental limit) during exercise in the heat different between: Children (ages 10-17 years) and adults (aged 18+). The research hypothesis is that: - Thermoregulatory strain (and the critical environmental limit for safe exercise) will be similar between children and adults when exercising at a fixed metabolic heat production of 220 W/kg.

Eligibility

Sex: Both males and femalesMin Age: 10 YearssMax Age: 40 Yearss

Plain Language Summary

Simplified for easier understanding

Public health guidelines warn that children are more vulnerable to heat-related illness during exercise than adults. However, most extreme heat policies treat children and adults the same way when deciding when to cancel or modify sport and exercise events. This study uses a carefully controlled laboratory environment to find out whether children and adults actually have different limits for safe exercise in hot and humid conditions. Participants exercise at a fixed, moderate intensity in a climate-controlled chamber while researchers precisely measure body temperature, sweat rate, and other indicators of how well the body is coping with the heat. By comparing these results between children (aged 10–17) and adults (aged 18–40), the study aims to determine whether different guidelines for the two age groups are scientifically justified. You may be eligible if you are aged 10 to 40 years old, are a non-smoker, and have no history of heart, lung, metabolic, or blood pressure conditions, diabetes, or related medications. Children need written consent from a parent or caregiver to participate. People with uncontrolled hypertension, diabetes complications, kidney or liver disease, anaemia, or thyroid abnormalities are not eligible.

This summary was AI-generated to explain the trial in plain language. It is not medical advice. Always discuss eligibility with your doctor before enrolling in a clinical trial.

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Interventions

Each participant (children aged 10-17) will take part in 2 experimental trials: a preliminary screening trial and a heat stress exposure. A minimum of 24 hours and will separate the two experimental

Each participant (children aged 10-17) will take part in 2 experimental trials: a preliminary screening trial and a heat stress exposure. A minimum of 24 hours and will separate the two experimental trials. Adherence to the experimental intervention will be confirmed by the researchers who will supervise participants throughout each experimental trial. During the preliminary trial participants will complete a submaximal exercise test on a treadmill consisting of four 4-mintute stages with the treadmill gradient increased at the end of each stage. During the second experimental trial, participants will complete a bout of exercise performed in a climate chamber set to 35°C (40% relative humidity). Initially, participants will complete 30-min of steady state treadmill exercise at a fixed metabolic heat production of 220 W/m2 measured using indirect calorimetry (Quark CPET, Cosmed). Once 30-min has elapsed, participants will continue exercising but the relatively humidity will be gradually (and continually) increased to 80% relative humidity over the next 50-min. Once an upward inflection in core body temperature is observed (as measured by an ingestible gastro-intestinal temperature pill) or once 60-min of exercise is completed, the trial will be terminated. Exercise will be terminated immediately if core temperature of 39.5°C is reached. However, if the participant feels uncomfortable at any time during testing, they can stop and withdraw from that session at any point, irrespective of their core temperature. During all trials (excluding preliminary trials) core body temperature, skin temperature, heat rate, local sweat rate and thermal perceptual responses will be monitored throughout.

Locations(1)

University of Sydney - Camperdown

NSW, Australia

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