Trial Review

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Trial registered on ANZCTR


Registration number
ACTRN12622000501741
Ethics application status
Approved
Date submitted
22/03/2022
Date registered
29/03/2022
Date last updated
3/02/2023
Date data sharing statement initially provided
29/03/2022
Type of registration
Prospectively registered

Titles & IDs
Public title
Is thermoregulatory capacity altered in children during exercise in hot weather?
Scientific title
Is thermoregulatory capacity altered in children? Defining the critical environmental limits for children exercising in heat stress conditions.
Secondary ID [1] 306738 0
None
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Heat related thermal strain 325732 0
Heat related cardiovascular strain 325733 0
Heat related changes in thermal perceptions (i.e., comfort and sensation) 325734 0
Condition category
Condition code
Injuries and Accidents 323075 323075 0 0
Other injuries and accidents
Public Health 323076 323076 0 0
Other public health
Cardiovascular 323077 323077 0 0
Normal development and function of the cardiovascular system

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
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.
Intervention code [1] 323185 0
Prevention
Intervention code [2] 323216 0
Early detection / Screening
Intervention code [3] 323217 0
Treatment: Other
Comparator / control treatment
The comparator is a cohort of health adult participants (+18 years). Adult participants will undergo the same two experimental trials as the child participants.
Control group
Active

Outcomes
Primary outcome [1] 330838 0
Core body temperature measure via telemetric gastrointestinal temperature pill:

The core temperature sensor (E-celcius, BodyCap™) will be used to assess gastrointestinal temperature. The sensor will be swallowed ~6 hours prior to arriving at the laboratory, so that the sensor has progressed past the stomach by the time the experimental session begins.
Timepoint [1] 330838 0
The time point at which inflection in core body temperature is observed between the start of exercise and the end of the humidity ramp protocol (i.e. timepoint between 0 and 120 min).
Primary outcome [2] 330839 0
Heart Rate

Heart rate will be measured continuously during the experimental visits via a Polar heart rate monitor.
Timepoint [2] 330839 0
The time point at which inflection in heart rate is observed between the start of exercise and the end of the humidity ramp protocol (i.e. timepoint between 0 and 120 min).
Primary outcome [3] 330840 0
Skin temperature

Skin temperature will be measured continuously during the exposures by taping 4 small sensors to the skin surface on the right side at the upper arm, chest, thigh and upper calf.
Timepoint [3] 330840 0
The time point at which inflection in core body temperature is observed between the start of exercise and the end of the humidity ramp protocol (i.e. timepoint between 0 and 120 min).
Secondary outcome [1] 407790 0
Whole body sweat rate

Participants will provide a nude weight (in private) before and immediately after the heat stress exposure on a calibrated digital scale. Whole-body sweat rate will be calculated as the difference in the pre and post weight, divided by the time between recorded weigh-ins.
Timepoint [1] 407790 0
Difference between pre- to post-heat exposure
Secondary outcome [2] 407791 0
Local sweat rate

Local sweat rate will be measured continuously during the study visits using a plastic capsule attached to the skin surface and ventilated with dry air on the upper left back.
Timepoint [2] 407791 0
The time point at which inflection in core body temperature is observed between the start of exercise and the end of the humidity ramp protocol (i.e. timepoint between 0 and 120 min).
Secondary outcome [3] 407792 0
Perceptual changes in thermal discomfort and thermal sensation
Thermal discomfort and thermal sensation will be measured at baseline and every 20 minutes during the heat exposure protocol using a visual analog scale.
Timepoint [3] 407792 0
20-min intervals throughout the heat stress exposure

Eligibility
Key inclusion criteria
Children: males and females aged 10 to 17.
Non-smokers with no history of respiratory, metabolic, cardiovascular, blood pressure disease, or of diabetes and not currently on any medication related to these conditions).
No difficult understanding or speaking English. Study participation consented by parent/caregiver with written assent obtained from child.

Adults: males and females aged 18 to 40.
Non-smokers with no history of respiratory, metabolic, cardiovascular, blood pressure disease, or of diabetes and not currently on any medication related to these conditions).
No difficult understanding or speaking English.
Minimum age
10 Years
Maximum age
40 Years
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
- Uncontrolled hypertension (greater than 180/110 mmHg).
- Uncontrolled diabetes or severe complications of diabetes.
- Evidence of severe renal disease, liver disease, cerebrovascular disease, pulmonary disease, endocrine abnormalities, cognitive impairment, psychiatric disorder, substance abuse, degenerative neurological condition or any other medical condition deemed to pose risk during the study visits.
- Medication known to cause hyper- or hypo-hidrosis (except those taken for hypertension).
- Currently taking a beta-blocker.
- Evidence of current fluid and electrolyte disorders
- Current diagnosis of anemia
- Abnormal thyroid function
- Significant cognitive impairment, psychiatric disorder, substance abuse, degenerative neurological condition
- Any other medical condition deemed to pose risk during the proposed testing or experiments.

Study design
Purpose of the study
Prevention
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation is not concealed
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Other
Other design features
Participants are split into two groups: 'Children' and 'Adults'. All participants will receive the same intervention.
Phase
Not Applicable
Type of endpoint/s
Safety
Statistical methods / analysis

Core temperature inflection point (humidity ramp 30 min onwards)

An upward inflection point in core temperature will be identified using segmental regression of Tcore with time during the humidity ramp part of the protocol. The critical humidity at which this upward inflection in Tcore is observed will be analysed using a 1-way mixed ANOVA employing the independent variable of age (4 levels: 10 to <12yrs, =12 to <15yrs, =15 to <18, adults (=18 to <40yrs). If significant main effects are found, between-group differences at individual time points will be assessed using independent samples t-tests. The significance level will be maintained at an alpha of 0.05 for all comparisons. All statistical analyses will be performed with GraphPad Prism (GraphPad Software, La Jolla, CA).

Recruitment
Recruitment status
Recruiting
Date of first participant enrolment
Anticipated
1/05/2022
Actual
1/05/2022
Date of last participant enrolment
Anticipated
31/12/2023
Actual
Date of last data collection
Anticipated
29/02/2024
Actual
Sample size
Target
48
Accrual to date
4
Final
Recruitment in Australia
Recruitment state(s)
NSW
Recruitment hospital [1] 22002 0
University of Sydney - Camperdown
Recruitment postcode(s) [1] 37106 0
2001 - Sydney
Recruitment postcode(s) [2] 37105 0
2006 - Camperdown

Funding & Sponsors
Funding source category [1] 311070 0
Government body
Name [1] 311070 0
National Health and Medical Research Council
Country [1] 311070 0
Australia
Primary sponsor type
University
Name
The University of Sydney
Address
The University of Sydney
Camperdown
NSW
2006
Country
Australia
Secondary sponsor category [1] 312406 0
None
Name [1] 312406 0
Address [1] 312406 0
Country [1] 312406 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 310613 0
The University of Sydney Human Research Ethics Committee
Ethics committee address [1] 310613 0
Research Integrity and Ethics Administration
Research Portfolio
Level 3, F23 Administration Building
The University of Sydney
Camperdown, NSW
2006
Ethics committee country [1] 310613 0
Australia
Date submitted for ethics approval [1] 310613 0
08/01/2020
Approval date [1] 310613 0
24/02/2020
Ethics approval number [1] 310613 0
2016/983

Summary
Brief 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.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 118266 0
Prof Ollie Jay
Address 118266 0
Thermal Ergonomics Laboratory, Room 901
Susan Wakil Health Building
The University of Sydney
Camperdown, NSW 2006
Country 118266 0
Australia
Phone 118266 0
+61 2 93519328
Fax 118266 0
Email 118266 0
ollie.jay@sydney.edu.au
Contact person for public queries
Name 118267 0
Prof Ollie Jay
Address 118267 0
Thermal Ergonomics Laboratory, Room 901
Susan Wakil Health Building
The University of Sydney
Camperdown, NSW 2006
Country 118267 0
Australia
Phone 118267 0
+61 2 93519328
Fax 118267 0
Email 118267 0
ollie.jay@sydney.edu.au
Contact person for scientific queries
Name 118268 0
Prof Ollie Jay
Address 118268 0
Thermal Ergonomics Laboratory, Room 901
Susan Wakil Health Building
The University of Sydney
Camperdown, NSW 2006
Country 118268 0
Australia
Phone 118268 0
+61 2 93519328
Fax 118268 0
Email 118268 0
ollie.jay@sydney.edu.au

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
Yes
What data in particular will be shared?
De-identified individual participant data will be available in published study results.
When will data be available (start and end dates)?
Immediately following publication - no end date.
Available to whom?
Within published journals and case by case at the discretion of the primary sponsor.
Available for what types of analyses?
Meta-analysis
How or where can data be obtained?
Access subject to approvals by the Principal Investigator with a requirement to sign data access agreements. Access can be obtained by emailing: ollie.jay@sydney.edu.au


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.