Effect of Exercise and Heat Stress on Acute Cardiometabolic Adaptations in Healthy Young Adults
March 6, 2025 updated by: Travis Gibbons, Northern Arizona University
Does Heat Stress Improve the Acute Metabolic and Cardiovascular Adaptations to Exercise
Life in space is completely void of physical and environmental stress.
It is well known that living things need regular physical stress (e.g.
exercise) to remain strong, functional and healthy.
More and more research is showing that regular environmental stress, for example heat and hypoxia, can further improve physical health.
Astronauts aboard the international space station (ISS) exercise for 1-2 hours every day to avoid physical deconditioning that would otherwise cause them to age rapidly in space.
Although physical exercise is very effective in remedying this deconditioning, today's astronauts still have physiological changes that indicate accelerated aging.
This is a cause for concern given NASA's priority to travel to mars within the next decade; a mission that will require at least double the duration in space for our astronauts.
The investigators think that the complete absence of environmental stress, i.e., heat, may be contributing to the accelerated aging that occurs during spaceflight.
Our study will assess the health effects of adding heat stress to exercise that could be performed in space by astronauts.
The goal is to inform best practice for astronauts to avoid physical deconditioning during long-duration spaceflight.
This information will also be relevant to life on earth as spaceflight is a model of inactivity here on earth.
Therefore, the potential benefits of adding heat stress will likely translate to life in space and on earth.
Study Overview
Status
Recruiting
Conditions
Intervention / Treatment
Detailed Description
Experimental procedures:
Participants will visit the lab on seven occasions. Participants will be required to practice regular exercise and dietary habits that can be easily replicated in the 24 hours prior to every laboratory visit. Exercise and dietary patterns will be documented during the first visit and thereafter the participants will be reminded of these practices and instructed to match them as closely as possible in the 24 hours leading up to all subsequent visits. Participants will only be instructed to avoid heavy exercise in the 12 hours prior to testing sessions. On the first visit, participants will be introduced into the lab, where the investigators will give oral and written instruction detailing the procedures and associated risks related to participating. Details of the experimental visits are outlined below:
Familiarization Visit (1 hour):
- Familiarization and fitness test
- Lactate threshold and maximal aerobic power test on an upright cycle ergometer.
Experimental visit #1 (6 hours):
- Control exercise, heated exercise or control rest
- Rectal or esophageal thermistor will be inserted.
- Venous cannula will be inserted by trained phlebotomist (Chloe Gustafson, Dr Travis Gibbons).
- Cycling exercise for 90 minutes at 90% of lactate threshold with 2 pedestal fans to maximize heat loss and prevent core temperature increase to <1 ̊ C.
- 2.5 hours of resting recovery in semi-supine position.
- Vascular assessment.
- Glucose tolerance test (blood will be sampled for glucose and insulin 15, 30, 60 and 120 minutes after consuming a mixed macronutrient meal)
- Rectal thermistor and venous cannula will be removed and participant will leave.
Experimental visit #2 (6 hours):
- Control exercise, heated exercise or control rest
- Complete identical procedures as experimental visit #2 with the following exceptions:
- Cycling exercise for 90 minutes at 90% of lactate threshold.
- No fans will be used to maximal heat gain.
- Participants will wear a water impermeable jacket, pants and gloves, and wear a winter hat (beanie).
- Core temperature will be allowed to rise naturally but exercise will stop if core temperature reaches 40 ̊ C.
Experimental visit #3 (6 hours):
- Control exercise, heated exercise or control rest
- Complete identical procedures as experimental visit #2 with the following exceptions:
- Participant will rest comfortably in the semi-supine position for 90 minutes.
Follow-up assessments after experimental visits 1, 2, and 3 (1 hour):
- Rectal or esophageal thermistor will be inserted.
- Participant will lie comfortably for 10 minutes.
- Arterial stiffness assessment will be performed (3 minutes)
- A venous blood sample will be collected.
- Participant will complete 5-minute blood volume assessment via carbon monoxide rebreathing technique.
- A final blood draw will be performed.
Study Type
Interventional
Enrollment (Estimated)
15
Phase
- Not Applicable
Contacts and Locations
This section provides the contact details for those conducting the study, and information on where this study is being conducted.
Study Contact
- Name: TRAVIS GIBBONS, PhD
- Phone Number: 928-523-4002
- Email: travis.gibbons@nau.edu
Study Locations
-
-
Arizona
-
Flagstaff, Arizona, United States, 86011
- Recruiting
- Northern Arizona University
-
Contact:
- TRAVIS GIBBONS, PhD
- Phone Number: 928-523-4002
- Email: travis.gibbons@nau.edu
-
-
Participation Criteria
Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.
Eligibility Criteria
Ages Eligible for Study
- Adult
Accepts Healthy Volunteers
Yes
Description
Inclusion Criteria:
-regularly physically active as determined via ParQ+
Exclusion Criteria:
- smokers
- bronchial asthma
- chronic obstructive pulmonary disease
- obese
- alcoholism
- requiring daily medications that may effect responses to exercise,
- anti-arrhythmogenics
- inhalers
- history of cardiovascular, respiratory, neurological, skeletal muscle disease
- irregular/absent menstrual cycle (females)
- unexpected responses to pre-experimental exercise tests
- previous diagnosis of heat stroke
Study Plan
This section provides details of the study plan, including how the study is designed and what the study is measuring.
How is the study designed?
Design Details
- Primary Purpose: Prevention
- Allocation: Randomized
- Interventional Model: Crossover Assignment
- Masking: Single
Arms and Interventions
Participant Group / Arm |
Intervention / Treatment |
|---|---|
|
Experimental: Exercise
Participants exercise for 90 minutes trying to remain cool with fans and limited clothing.
|
Exercise for 90 minutes (cycling) while minimizing thermal strain
Exercise for 90 minutes (cycling) while maximizing thermal strain
|
|
Experimental: Heat strain
Participants exercise for 90 minutes wearing winter and rain clothes to develop heat strain.
|
Exercise for 90 minutes (cycling) while minimizing thermal strain
Exercise for 90 minutes (cycling) while maximizing thermal strain
|
|
Placebo Comparator: Control
Resting control for 90 minutes.
Not allowed to exercise.
|
Exercise for 90 minutes (cycling) while minimizing thermal strain
Exercise for 90 minutes (cycling) while maximizing thermal strain
|
What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Glucose tolerance
Time Frame: 2 hours after intervention complete
|
Glucose to insulin concentration ratio in serum.
|
2 hours after intervention complete
|
Secondary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Arterial compliance
Time Frame: 2 hours after intervention complete
|
Change in artery diameter (millimeter) assessed via ultrasound per change in artery pressure (mm Hg) assessed via tonometry.
|
2 hours after intervention complete
|
|
Plasma volume expansion
Time Frame: 24 hours after intervention
|
Plasma volume change measured with carbon monoxide rebreathe
|
24 hours after intervention
|
Collaborators and Investigators
This is where you will find people and organizations involved with this study.
Sponsor
Study record dates
These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.
Study Major Dates
Study Start (Actual)
March 1, 2025
Primary Completion (Estimated)
December 31, 2025
Study Completion (Estimated)
May 21, 2026
Study Registration Dates
First Submitted
February 24, 2025
First Submitted That Met QC Criteria
March 6, 2025
First Posted (Actual)
March 25, 2025
Study Record Updates
Last Update Posted (Actual)
March 25, 2025
Last Update Submitted That Met QC Criteria
March 6, 2025
Last Verified
February 1, 2025
More Information
Terms related to this study
Additional Relevant MeSH Terms
Other Study ID Numbers
- 2224584
Plan for Individual participant data (IPD)
Plan to Share Individual Participant Data (IPD)?
NO
IPD Plan Description
I am concerned for privacy protection of our participants.
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
No
Studies a U.S. FDA-regulated device product
No
product manufactured in and exported from the U.S.
No
This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.