Impact of Indoor Overheating on Physiological Strain in Children

A Preliminary Study Assessing the Effectiveness of a 26 °C Indoor Temperature Limit on Physiological Responses in Children

Communities worldwide are experiencing increasing heat extremes that challenge the limits of human thermoregulation, particularly among vulnerable populations such as children. Compared with adults, children are more susceptible to heat related illness due to less efficient thermoregulatory systems and difficulty recognizing early signs of heat stress. In addition, prolonged heat exposure can adversely affect their mental health, contributing to cognitive decline, heightened anxiety, and irritability. As children spend substantial time in hot environments at school and at home, and as these conditions intensify with climate change, actions to safeguard their health are essential. Yet our understanding of heat exposure effects in children remains incomplete, hindering the development of evidence based strategies to protect them.

To address this gap, the investigators aim to evaluate whether an indoor temperature limit of 26 °C (45 percent relative humidity), the upper threshold recommended to protect older adults, can effectively prevent dangerous increases in physiological strain and declines in cognitive function in children during a simulated daylong heatwave. The preliminary study will assess physiological and cognitive responses in children aged 10 to 15 years during a 6 hour exposure (approximating a typical school day) to two conditions: (1) the recommended indoor temperature upper limit (26 °C) and (2) a high heat condition representative of homes and schools without air conditioning during extreme heat events (36 °C). In both conditions, children will remain seated at rest while wearing light clothing (t shirt and shorts), with the exception of performing 15 minutes of stepping exercise (6-6.5 METS) each hour (excluding the lunch period) to reflect typical daily activity in a school setting. This experimental design will allow investigators to determine whether maintaining indoor temperatures at the recommended upper limit for older adults sufficiently mitigates physiological strain in children.

Study Overview

• Status: Recruiting
• Conditions: Cognitive Change; Physiological Stress; Heat Stress
• Intervention / Treatment: Other: Simulated exposure to indoor overheating

• Study Type: Interventional
• Enrollment (Estimated): 10
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Glen P Kenny, PhD; Phone Number: 4282 613-562-5800; Email: gkenny@uottawa.ca

Study Locations

• Canada
  • Ontario
    • Ottawa, Ontario, Canada, K1N 6N5
      • Recruiting
      • University of Ottawa
      • Contact: Glen P Kenny, PhD; Phone Number: 4282 613-562-5800; Email: gkenny@uottawa.ca

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• English or French speaking.
• Ability to provide informed assent.

Exclusion Criteria:

• Chronic health conditions
• Endurance exercise training (greater than 3 sessions of vigorous exercise training per week for 30 minutes or more)
• Restrictions to physical activity

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Exposure to indoor temperature upper limit of 26°C; Participants exposed daylong (6 hours) to an indoor temperature maintained at 26°C and 45% relative humidity (humidex equivalent of 29).	Other: Simulated exposure to indoor overheating; Children exposed to a 6-hour simulated heat exposure
Experimental: Exposure to hot indoor environment of 36°C; Participants exposed daylong (6 hours) to an indoor temperature maintained at 36°C and 45% relative humidity (humidex equivalent of 45).	Other: Simulated exposure to indoor overheating; Children exposed to a 6-hour simulated heat exposure

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Core temperature (Peak) during daylong exposure to indoor overheating	Peak visceral temperature (15 min average) during exposure. Visceral temperature is measured continuously throughout the 6 hour exposure to the simulated indoor overheating.	End of 6 hour daylong exposure

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mean skin temperature (Peak) during daylong exposure to indoor overheating	Peak mean skin temperature (15 min average) during exposure. Mean skin temperature as calculated from skin temperature measured across 7 body regions is measured continuously throughout the 6 hour exposure to the simulated indoor overheating.	End of 6 hour daylong exposure
Mean skin temperature (AUC) during daylong exposure to indoor overheating	Areas under the curve (AUC) of mean skin temperature as calculated over 7 body regions during the 6 hour exposure to the simulate indoor overheating.	End of 6 hour daylong exposure
Mean skin temperature end of daylong exposure to indoor overheating	Mean skin temperature measured over 7 body regions at hour 6 of exposure to indoor overheating (15-min average).	End of 6 hour daylong exposure
Heat rate (Peak) during daylong exposure to indoor overheating	Peak heart rate (15 min average) during exposure. Heart rate is measured continuously throughout the 6 hour exposure to the simulated indoor overheating.	End of 6 hour daylong exposure
Heart rate (AUC) during daylong exposure to indoor overheating	Areas under the curve (AUC) of heart rate during the 6 hour exposure to the simulate indoor overheating.	End of 6 hour daylong exposure
Heart rate end of daylong exposure to indoor overheating	Heart rate measured at hour 6 of exposure to indoor overheating (15-min average).	End of 6 hour daylong exposure
Systolic blood pressure during daylong exposure to indoor overheating	Systolic blood pressure measured in triplicate via automated oscillometry (~60 seconds between measures).	At the start (hour 0) and end of 6 hour daylong exposure
Diastolic blood pressure during daylong exposure to indoor overheating.	Diastolic blood pressure measured in triplicate via automated oscillometry (~60 seconds between measures).	At the start (hour 0) and end of 6 hour daylong exposure
Reaction time during daylong exposure to indoor overheating (cognitive function).	Participants will be provided with a tablet device with the Sway Medical testing platform for the assessment of reaction time. Participants will be asked to initiate a movement of the device in response to a visual cue.	At the start (hour 0) and end of 6 hour daylong exposure
Impulse control during daylong exposure to indoor overheating (cognitive function).	Participants will be provided with a tablet device with the Sway Medical testing platform for the assessment of impulse control. Participants will be asked to respond to both "go" and "no-go" visual cues. In response to the "go" cue, participants will initiate a movement of the device.	At the start (hour 0) and end of 6 hour daylong exposure
Memory recall during daylong exposure to indoor overheating (cognitive function).	Participants will be provided with a tablet device with the Sway Medical testing platform for the assessment of memory recall. Participants complete both a delayed recall test and a working memory test.	At the start (hour 0) and end of 6 hour daylong exposure
CDC 4-Stage Balance Test during daylong exposure to indoor overheating (postural stability).	To assess postural stability, participants hold a tablet to their chest, then auditory cues guide participants through four consecutive stances, feet side by side, instep of one foot touching the big toe of the other foot, tandem stand with one foot in front of the other, heel touching toe, and stand on one foot. The balance assessment will be evaluated based on movement detected by an accelerometer integrated into the hardware of the tablet device (Sway Medical Inc).	At the start (hour 0) and end of 6 hour daylong exposure
Executive function during daylong exposure to indoor overheating (cognitive function).	Participants will be provided with a tablet device with the Sway Medical testing platform for the assessment of executive function. Participants will complete the Cued Stroop test, in which they are presented a sequence of congruent, neutral and incongruent color-word tasks.	At the start (hour 0) and end of 6 hour daylong exposure
BTrackS Balance Assessment during daylong exposure to indoor overheating (postural stability).	To assess postural stability, participants will be asked to stand on a BTracks force plate with their feet spread out to shoulder width, hand on their hips and eyes closed. The assessment will comprise of four trials (one practice trial) lasting 20 seconds in length and 20 seconds between trials. Center of pressure (COP) vector data along vertical (y) and horizontal (x) axes will be summed for the total path excursion length (cm) during each trial	At the start (hour 0) and end of 6 hour daylong exposure
Hydration status during daylong exposure to indoor overheating	Hydration status measured via assessing the urine specific gravity of a urine sample.	At the start (hour 0) and end of 6 hour daylong exposure
Fluid consumption during daylong exposure to indoor overheating	Average hourly fluid consumption calculated by weighing participant water intake at the start and end of each hour of exposure (normalized to the exposure duration).	At end of 6 hour daylong exposure
Fluid loss during daylong exposure to indoor overheating	Fluid loss calculated as the change in body mass during each exposure presented as a percentage of baseline body mass (corrected for food consumption).	At end of 6 hour daylong exposure
Thermal sensation scale during daylong exposure to indoor overheating	Thermal sensation assessed via a visual analog scale (How hot do you feel?) ranging from "extremely hot" to "neutral".	At the start (hour 0) and end of 6 hour daylong exposure
Thermal sensation 2 scale during daylong exposure to indoor overheating	Thermal sensation assessed via a visual analog scale ("How do you feel?") ranging from "hot" to "cold"(midpoint: neutral)	At the start (hour 0) and end of 6 hour daylong exposure
Thermal comfort scale during daylong exposure to indoor overheating	Thermal comfort assessed via a visual analog scale ("How comfortable does your body temperature feel?") ranging from "very uncomfortable" to "comfortable".	At the start (hour 0) and end of 6 hour daylong exposure
Thirst sensation scale during daylong exposure to indoor overheating	Thirst sensation assessed via a visual analog scale ranging from very, very thirsty to not thirsty at all.	At the start (hour 0) and end of 6 hour daylong exposure
Feel good scale during daylong exposure to indoor overheating	Feel good scale assessed via a visual analog scale (How good do you feel?) ranging from "very good" to "very bad" (midpoint: neutral)	At the start (hour 0) and end of 6 hour daylong exposure
Activity levels during daylong exposure to indoor overheating	Activity levels assessed via a wearable monitor (Actical) containing an accelerometer worn on the wrist and hip.	End of 6 hour daylong exposure
Perceived exertion scale during daylong exposure to indoor temperature limit.	Perceived exertional assessed via a visual analog scale ("How hard are you working?") ranging from "no exertional at all" to "maximal exertion"	At the start (hour 0) and end of 6 hour daylong exposure
Profiles of Mood States (POMS) during daylong exposure to indoor overheating	Potential changes in mood (7 subscales of mood: tension, anger, depression, fatigue, confusion, vigor and esteem related affect). The POMS-40 is a validated, self-administered questionnaire that examines seven distinct aspects of mood state across two positive subscales (Esteem-Related Affect, and Vigor) and five negative subscales (Fatigue, Tension, Confusion, Anger, and Depression), which are described across 40 distinct adjectives. For each individual item, participants were asked to describe "how you feel right now" by responding using a 5-point Likert scale (0 = "Not at all", 1 = "A little", 2 = "Moderately", 3 = "Quite a lot", or 4 = "Extremely"). The values of items associated with a specific subscale (e.g., Fatigue) were summed to calculate its score.	At the start (hour 0) and end of 6 hour daylong exposure
Environmental Symptoms Questionnaire (ESQ) during daylong exposure to indoor overheating	Self-reported environmental reactions and medical symptomatology associated with prolonged heat exposure. The ESQ-IV is a validated 68-item, self-administered questionnaire that has been used successfully in identifying symptomatology during exposure to a wide variety of environmental conditions, including heat exposure. Participants are asked to assess and described "how you have been feeling today" by responding to each item using a 6-point Likert scale (0 = "Not at all", 1 = "Slight", 2 = "Somewhat", 3 = "Moderate", 4 = "Quite a bit", or 5 = "Extreme"). Total Symptom Score was calculated from this data by taking the sum of the intensity ratings from all 68 individual items using reverse scores for the three positive items from the list ("I Felt Good", "I Felt Alert", and "I Felt Wide Awake").	At the start (hour 0) and end of 6 hour daylong exposure
Core temperature (AUC) during daylong exposure to indoor overheating	Areas under the curve (AUC) of visceral temperature during the 6 hour exposure to the simulate indoor overheating.	End of 6 hour daylong exposure
Core temperature end of daylong exposure to indoor overheating	Visceral temperature measured at hour 6 of exposure to indoor overheating (15-min average).	End of 6 hour daylong exposure

Collaborators and Investigators

• Sponsor: University of Ottawa
• Investigators: Principal Investigator: Glen P Kenny, PhD, University of Ottawa

Study record dates

Study Major Dates

• Study Start (Actual): November 8, 2025
• Primary Completion (Estimated): June 1, 2026
• Study Completion (Estimated): December 31, 2026

Study Registration Dates

• First Submitted: November 21, 2025
• First Submitted That Met QC Criteria: November 21, 2025
• First Posted (Actual): December 3, 2025

Study Record Updates

• Last Update Posted (Actual): April 23, 2026
• Last Update Submitted That Met QC Criteria: April 20, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Adolescent; Physical activity; Thermoregulation; Youth; Hyperthermia; Heat wave; Heat strain; Thermal comfort; Indoor temperatures; Indoor overheating; Heat vulnerability
• Additional Relevant MeSH Terms: Wounds and Injuries; Body Temperature Changes; Pathological Conditions, Signs and Symptoms; Behavior; Signs and Symptoms; Hyperthermia; Heat Stress Disorders; Motor Activity
• Other Study ID Numbers: HEPRU-2025-10-A

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No