NCT05838612

Hot Water Immersion as a Heat Acclimation Strategy in Older Adults

Completed NA Last updated 11 July 2024

What this trial tests

NA trial testing Heat acclimation in Hyperthermia in 12 participants. Completed in 16 February 2023.

Timeline

29 April 2022

Primary endpoint
16 February 2023

16 February 2023

Quick facts

Lead sponsor	University of Ottawa
Phase	NA
Status	Completed
Study type	INTERVENTIONAL
Allocation	na
Design	single group
Masking	none
Primary purpose	basic science
Enrollment	12
Start date	29 April 2022
Primary completion	16 February 2023
Estimated completion	16 February 2023
Sites	1 location across Canada

Drugs / interventions tested

• Heat acclimation

Conditions studied

• Hyperthermia — all drugs for Hyperthermia →
• Heat Exposure — all drugs for Heat Exposure →
• Heat Stress — all drugs for Heat Stress →
• Thermoregulation — all drugs for Thermoregulation →

Sponsor

University of Ottawa

Who can join

Adults 60 to 80, male only, with Hyperthermia or Heat Exposure. Patients with the condition only — healthy volunteers not accepted.

Sponsor's own description

Aging is associated with impairments in heat loss responses of skin blood flow and sweating leading to reductions in whole-body heat loss. Consequently, older adults store more body heat and experience greater elevations in core temperature during heat exposure at rest and during exercise. This maladaptive response occurs in adults as young as 40 years of age. Recently, heat acclimation associated with repeated bouts of exercise in the heat performed over 7 successive days has been shown to enhance whole-body heat loss in older adults, leading to a reduction in body heat storage. However, performing exercise in the heat may not be well tolerated or feasible for many older adults. Passive heat acclimation, such as the use of warm-water immersion may be an effective, alternative method to enhance heat-loss capacity in older adults. Thus, the following study aims to assess the effectiveness of a 7-day warm-water immersion (\~40°C) protocol in enhancing whole-body heat loss in older adults. Warm-water immersion will consist of a one-hour immersion in warm water with core temperature clamped at 38.5°C. Improvements in whole-body heat loss will be assessed during an incremental exercise protocol performed in dry heat (i.e., 40°C, \~15% relative humidity) prior to and following the 7-day passive heat acclimation protocol. The incremental exercise protocol will consist of three 30 minute exercise bouts performed at increasing fixed rates of metabolic heat production (i.e., 150, 200, and 250 W/m2), each separated by 15-minutes of recovery, with exception final recovery will be 1-hour in duration) performed in a direct calorimeter (a device that provides a precise measurement of the heat dissipated by the human body).

Publications & conference data

1 peer-reviewed publication reference this trial (live from Europe PMC):

1. The influence of heat acclimation on the relation and agreement between perceptual and physiological strain in older males during exercise-heat stress.
   Janetos K, O'Connor F, Morris N, Kenny G. · · 2026 · PMID 41549363 · DOI 10.1139/apnm-2025-0360