Skip to main content
OpenTrials
Completed

NCT Number: NCT05838612

Hot Water Immersion as a Heat Acclimation Strategy in Older Adults

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).

Completed

Looking for future studies?

Notify Me

Key information

Conditions

Hyperthermia Aging Body Temperature Changes Heat Exposure Heat Stress Heat Stress Disorders Pathological Conditions, Signs and Symptoms Signs and Symptoms Thermoregulation Wounds and Injuries

Age range

60 year–80 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Univerisity of Ottawa

Ottawa, Ontario, K1N6N5, Canada

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Elderly (60-80 years), non-smoking adults.
  • Not engaged in regular physical activity (>2 sessions/week for ≥20 minutes per session).
  • Willing to provide informed consent.
  • Healthy, no diagnosed health conditions.
  • Body Mass index (BMI) <35 kg/m2.

Exclusion criteria

  • Heat adapted due to repeated exposure to hot environments within the last 3 weeks (use sauna, recent travel to hot climates, other).

Treatment and study plan

Heat acclimation

Other

Participants will complete a 7-day passive heat acclimation protocol consisting of immersion in warm water (~40°C) for 1 hour over 7 consecutive days.

Primary outcomes

  1. Evaporative heat loss

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Evaporative heat loss as assessed using a direct air calorimeter.

  2. Evaporative heat loss

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Evaporative heat loss as assessed using a direct air calorimeter.

  3. Evaporative heat loss

    Time frame: End of 30 minute bout 3 (average of last 5 minutes).

    Evaporative heat loss as assessed using a direct air calorimeter.

  4. Whole-body heat loss

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    The sum of evaporative and dry heat exchange will be quantified during each exercise period (i.e., 150, 200 and 250 W/m2).

  5. Whole-body heat loss

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    The sum of evaporative and dry heat exchange will be quantified during each exercise period (i.e., 150, 200 and 250 W/m2).

  6. Whole-body heat loss

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    The sum of evaporative and dry heat exchange will be quantified during each exercise period (i.e., 150, 200 and 250 W/m2).

Secondary outcomes

  1. Body heat storage

    Time frame: Change from start to end of 30 minute exercise bout 1

    Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.

  2. Body heat content

    Time frame: Change from start to end of 30 minute exercise bout 2

    Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.

  3. Body heat storage

    Time frame: Change from start to end of 30 minute exercise bout 3

    Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.

  4. Cumulative body heat storage

    Time frame: Change from baseline resting to end of exercise bout 3

    Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.

  5. Dry heat loss

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Dry heat loss as assessed using a direct air calorimeter.

  6. Dry heat loss

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Dry heat loss as assessed using a direct air calorimeter.

  7. Dry heat loss

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Dry heat loss as assessed using a direct air calorimeter.

  8. Core temperature

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Core temperature indexed by rectal/visceral temperature

  9. Core temperature

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Core temperature indexed by rectal/visceral temperature

  10. Core temperature

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Core temperature indexed by rectal/visceral temperature

  11. Change in core temperature

    Time frame: Change from baseline resting to end of end of 30 minute exercise bout 3.

    Core temperature indexed by rectal/visceral temperature

  12. Skin temperature

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Skin temperature measured at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - upper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%.

  13. Skin temperature

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Skin temperature measured at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - upper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%.

  14. Skin temperature

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Skin temperature measured at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - upper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%.

  15. Change in skin temperature

    Time frame: Change from baseline resting to end of end of 30 minute exercise bout 3.

    Skin temperature measured at 4-sites (chest, upper arm, thigh, calf) with mean value calculated as weighted value of 4 sites - upper arm, 30%; chest, 30%; thigh, 20%; and calf, 20%.

  16. Heart rate

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Measured continuously with chest-band device

  17. Heart rate

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Measured continuously with chest-band device

  18. Heart rate

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Measured continuously with chest-band device

  19. Heart rate variability

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains

  20. Heart rate variability

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains

  21. Heart rate variability

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains

  22. Thermal comfort scale

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Thermal comfort assessed via a questionnaire using the ASHRAE 4-point scale ("1=comfortable to 4=very uncomfortable")

  23. Thermal comfort scale

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Thermal comfort assessed via a questionnaire using the ASHRAE 4-point scale ("1=comfortable to 4=very uncomfortable")

  24. Thermal comfort scale

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Thermal comfort assessed via a questionnaire using the ASHRAE 4-point scale ("1=comfortable to 4=very uncomfortable")

  25. Thermal sensation scale

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Thermal sensation will be assessed using the ASHRAE 7-point scale ("0=neutral to 7=extremely hot")

  26. Thermal sensation scale

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Thermal sensation will be assessed using the ASHRAE 7-point scale ("0=neutral to 7=extremely hot")

  27. Thermal sensation scale

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Thermal sensation will be assessed using the ASHRAE 7-point scale ("0=neutral to 7=extremely hot")

  28. Thirst sensation scale

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Thirst sensation will be quantified using a 9-point scale ("1=not thirsty at all to 9=very, very thirsty")

  29. Thirst sensation scale

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Thirst sensation will be quantified using a 9-point scale ("1=not thirsty at all to 9=very, very thirsty")

  30. Thirst sensation scale

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Thirst sensation will be quantified using a 9-point scale ("1=not thirsty at all to 9=very, very thirsty")

  31. Rating of perceived exertion

    Time frame: End of 30 minute exercise bout 1 (average of last 5 minutes).

    Rating of perceived exertion will be quantified using a 14-point scale ("6=no exertion at all to 20=maximal exertion")

  32. Rating of perceived exertion

    Time frame: End of 30 minute exercise bout 2 (average of last 5 minutes).

    Rating of perceived exertion will be quantified using a 14-point scale ("6=no exertion at all to 20=maximal exertion")

  33. Rating of perceived exertion

    Time frame: End of 30 minute exercise bout 3 (average of last 5 minutes).

    Rating of perceived exertion will be quantified using a 14-point scale ("6=no exertion at all to 20=maximal exertion")

Sponsors and collaborators

Lead sponsor

University of Ottawa

Other

Registry information

Official study title

Short-term Warm Water Immersion as a Heat Acclimation Strategy to Enhance Heat Dissipation in Older Adults: An Exploratory Study

Important dates

Study start
2022
Primary completion
2023
Study completion
2023
First posted
May 1, 2023
Registry last updated
Jul 11, 2024

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.