Recruiting

Physiological Strain

Sponsor:

University of Ottawa

Code:

NCT07267598

Conditions

Heat Stress

Physiological Stress

Cognitive Change

Eligibility Criteria

Sex: All

Age: 18 - 29

Healthy Volunteers: Not accepted

Interventions

Simulated indoor temperature upper limit

Study Details

Brief summary:

While an indoor upper temperature limit of 26 °C has been shown to protect heat-vulnerable older adults (DOI: 10.1289/EHP11651), this guideline has not been verified in young, habitually active adults. Public health recommendations during hot weather typically emphasize staying in cool environments, avoiding strenuous activity, wearing lightweight clothing, and maintaining adequate hydration. However, young adults may be less likely to follow these guidelines. They often do not reduce their physical activity during extreme heat events and may overdress for fashion, cultural, or religious reasons. These behaviors can impose an additional thermoregulatory burden and lead to greater physiological strain during heat exposure, even though young adults generally have a higher capacity for heat dissipation than older individuals. Accordingly, it is important to evaluate whether an indoor temperature limit of 26 °C is sufficient to protect young, habitually active adults.

To address this gap, the investigators aim to assess changes in body temperature and cardiovascular strain in young, habitually active adults (18-29 years) during an 8-hour exposure to the recommended indoor upper temperature limit of 26 °C and 45% relative humidity (humidex of 29, considered comfortable). Participants will complete two conditions:

A) seated rest while dressed in light clothing (T-shirt, shorts, and socks), and B) light exercise (stepping to simulate activities of daily living, 4-4.5 METs) performed once per hour (except for the lunch hour) while dressed in light clothing plus an additional insulating layer (sweatshirt and sweatpants).

This experimental design will allow investigators to determine the effects of added clothing insulation and light activity-representative of typical daily behaviors-on physiological strain in young adults, and to assess whether refinements to the recommended 26 °C indoor temperature limit are warranted for this population.

Conditions

Heat Stress

Physiological Stress

Cognitive Change

Study ID

NCT07267598

Start date

Nov 7, 2025

Status verified date

Jun, 2026

Completion date

Dec 30, 2026

Anticipated

Primary completion date

Jan 25, 2026

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18 - 29

Healthy Volunteers: Not accepted

Inclusion Criteria:

  • Non-smoking.
  • English or French speaking.
  • Ability to provide informed consent.
  • Healthy young adults without chronic disease (e.g., type 1 diabetes, hypertension)

Exclusion Criteria:

  • Endurance trained (i.e., engaged in regular physical training activities more than 3 times a week for more than 1 hour per session).
  • Undergoing passive heat exposures such as regular of saunas, warm-water immersion, other.
  • Use of or changes in medication judged by the patient or investigators to make participation in this study inadvisable.
  • Current pregnancy

Study Design

Enrollment

10 participants

Anticipated

Allocation

Randomized

Intervention Model

Crossover

Primary purpose

Basic Science

Interventions and Outcome Measures

Arms

experimental: Exposure to indoor temperature upper limit without physical activity and added clothing.

Participants, dressed in light clothing (t-shirt, shorts and socks), perform seated rest while exposed daylong (8 hours) to an indoor temperature maintained at 26°C and 45% relative humidity (humidex equivalent of 29).

experimental: Exposure to indoor temperature upper limit with physical activity and added clothing.

Participants, dressed in light clothing (t-shirt, shorts and socks) and an added clothing layer (sweatshirt and sweatpants), perform light exercise (i.e., stepping, representing activities of daily living, 4-4.5 METS) every hour (with exception of lunch hour) while exposed daylong (8 hours) to an indoor temperature maintained at 26°C and 45% relative humidity (humidex equivalent of 29).

Interventions

Simulated indoor temperature upper limit

Young adults exposed to an 8-hour simulated exposure.

Primary outcome measure

  • Core temperature (Peak) during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Core temperature (AUC) during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Core temperature end of daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Mean skin temperature (Peak) during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Mean skin temperature (AUC) during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Mean skin temperature end of daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Heat rate (Peak) during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Heart rate (AUC) during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Heart rate end of daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Heart rate variability: RMSSD during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Heart rate variability: SDNN during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Cardiac response to standing from supine (30:15 ratio) during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Systolic response to standing from supine during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Systolic blood pressure during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Diastolic blood pressure during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Rate pressure product during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Reaction time during daylong exposure to indoor temperature limit (cognitive function). [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Impulse control during daylong exposure to indoor temperature limit (cognitive function). [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • CDC 4-Stage Balance Test during daylong exposure to indoor temperature limit (postural stability). [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • BTrackS Balance Assessment during daylong exposure to indoor temperature limit (postural stability). [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Fluid consumption during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Fluid loss during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Change in plasma volume during daylong exposure to indoor temperature limit. [ Time Frame: End of 8 hour daylong exposure ]
  • Thermal comfort scale during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Thirst sensation scale during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Arousal scale during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Thermal sensation scale during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Thermal sensation 2 scale during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Orthostatic intolerance symptoms assessment during daylong exposure to indoor temperature limit. [ Time Frame: At end of 8 hour daylong exposure ]
  • Feel good scale during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Perceived exertion scale during daylong exposure to indoor temperature limit. [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Hydration status during daylong exposure to indoor overheating [ Time Frame: At the start (hour 0) and end of 8 hour daylong exposure ]
  • Activity levels during daylong exposure to indoor overheating [ Time Frame: End of 8 hour daylong exposure ]

Central Contacts and Locations

Central contacts

Glen P Kenny, PhD

6133029267gkenny@uottawa.ca

Locations

University of Ottawa

Recruiting

Ottawa, Ontario, Canada, K1N 6N5

Contacts

Glen P Kenny, PhD

613-562-5800gkenny@uottawa.ca

More Information

Sponsor

University of Ottawa

Last update posted

Jun 16, 2026

Last verified

Jun, 2026

Keywords

  • Indoor overheating
  • Indoor temperatures
  • Heat wave
  • Thermoregulation
  • Heat strain
  • Heat vulnerability
  • Hyperthermia
  • Thermal comfort
  • Activities of daily living
  • Clothing insulation

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-10. This information was provided to ClinicalTrials.gov by University of Ottawa on 2026-06-16.