Hot Water Immersion as a Heat Acclimation Strategy in Older Adults

Aging Clinical Trial

Official title:

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

Clinical Trial Details — Status: Active, not recruiting

Administrative data

• NCT number: NCT05838612
• Other study ID #: HEPRU-2023-02
• Status: Active, not recruiting
• Phase: N/A
• Start date: April 29, 2022
• Est. completion date: June 30, 2023

Study information

• Verified date: April 2023
• Source: University of Ottawa
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

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).

Recruitment information / eligibility

• Status: Active, not recruiting
• Enrollment: 12
• Est. completion date: June 30, 2023
• Est. primary completion date: February 16, 2023
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Male
• Age group: 60 Years to 80 Years

Eligibility

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).

Related Conditions & MeSH terms

• Aging
• Heat Exposure
• Heat Stress
• Hyperthermia
• Thermoregulation

Intervention

Other:
• Heat acclimation
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.

Locations

Country	Name	City	State
Canada	Univerisity of Ottawa	Ottawa	Ontario

Sponsors (1)

Lead Sponsor	Collaborator
University of Ottawa

Country where clinical trial is conducted

Canada, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Evaporative heat loss	Evaporative heat loss as assessed using a direct air calorimeter.	End of 30 minute exercise bout 1 (average of last 5 minutes).
Primary	Evaporative heat loss	Evaporative heat loss as assessed using a direct air calorimeter.	End of 30 minute exercise bout 2 (average of last 5 minutes).
Primary	Evaporative heat loss	Evaporative heat loss as assessed using a direct air calorimeter.	End of 30 minute bout 3 (average of last 5 minutes).
Primary	Whole-body heat loss	The sum of evaporative and dry heat exchange will be quantified during each exercise period (i.e., 150, 200 and 250 W/m2).	End of 30 minute exercise bout 1 (average of last 5 minutes).
Primary	Whole-body heat loss	The sum of evaporative and dry heat exchange will be quantified during each exercise period (i.e., 150, 200 and 250 W/m2).	End of 30 minute exercise bout 2 (average of last 5 minutes).
Primary	Whole-body heat loss	The sum of evaporative and dry heat exchange will be quantified during each exercise period (i.e., 150, 200 and 250 W/m2).	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Body heat storage	Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.	Change from start to end of 30 minute exercise bout 1
Secondary	Body heat content	Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.	Change from start to end of 30 minute exercise bout 2
Secondary	Body heat storage	Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.	Change from start to end of 30 minute exercise bout 3
Secondary	Cumulative body heat storage	Cumulative amount of heat stored within the body calculated as the temporal summation of metabolic heat production and net heat loss.	Change from baseline resting to end of exercise bout 3
Secondary	Dry heat loss	Dry heat loss as assessed using a direct air calorimeter.	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Dry heat loss	Dry heat loss as assessed using a direct air calorimeter.	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Dry heat loss	Dry heat loss as assessed using a direct air calorimeter.	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Core temperature	Core temperature indexed by rectal/visceral temperature	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Core temperature	Core temperature indexed by rectal/visceral temperature	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Core temperature	Core temperature indexed by rectal/visceral temperature	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Change in core temperature	Core temperature indexed by rectal/visceral temperature	Change from baseline resting to end of end of 30 minute exercise bout 3.
Secondary	Skin temperature	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%.	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Skin temperature	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%.	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Skin temperature	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%.	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Change in skin temperature	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%.	Change from baseline resting to end of end of 30 minute exercise bout 3.
Secondary	Heart rate	Measured continuously with chest-band device	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Heart rate	Measured continuously with chest-band device	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Heart rate	Measured continuously with chest-band device	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Heart rate variability	Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Heart rate variability	Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Heart rate variability	Measures of variability computed from the time, frequency, time-frequency, scale-invariant, entropy, and other nonlinear domains	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Thermal comfort scale	Thermal comfort assessed via a questionnaire using the ASHRAE 4-point scale ("1=comfortable to 4=very uncomfortable")	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Thermal comfort scale	Thermal comfort assessed via a questionnaire using the ASHRAE 4-point scale ("1=comfortable to 4=very uncomfortable")	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Thermal comfort scale	Thermal comfort assessed via a questionnaire using the ASHRAE 4-point scale ("1=comfortable to 4=very uncomfortable")	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Thermal sensation scale	Thermal sensation will be assessed using the ASHRAE 7-point scale ("0=neutral to 7=extremely hot")	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Thermal sensation scale	Thermal sensation will be assessed using the ASHRAE 7-point scale ("0=neutral to 7=extremely hot")	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Thermal sensation scale	Thermal sensation will be assessed using the ASHRAE 7-point scale ("0=neutral to 7=extremely hot")	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Thirst sensation scale	Thirst sensation will be quantified using a 9-point scale ("1=not thirsty at all to 9=very, very thirsty")	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Thirst sensation scale	Thirst sensation will be quantified using a 9-point scale ("1=not thirsty at all to 9=very, very thirsty")	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Thirst sensation scale	Thirst sensation will be quantified using a 9-point scale ("1=not thirsty at all to 9=very, very thirsty")	End of 30 minute exercise bout 3 (average of last 5 minutes).
Secondary	Rating of perceived exertion	Rating of perceived exertion will be quantified using a 14-point scale ("6=no exertion at all to 20=maximal exertion")	End of 30 minute exercise bout 1 (average of last 5 minutes).
Secondary	Rating of perceived exertion	Rating of perceived exertion will be quantified using a 14-point scale ("6=no exertion at all to 20=maximal exertion")	End of 30 minute exercise bout 2 (average of last 5 minutes).
Secondary	Rating of perceived exertion	Rating of perceived exertion will be quantified using a 14-point scale ("6=no exertion at all to 20=maximal exertion")	End of 30 minute exercise bout 3 (average of last 5 minutes).