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Completed

NCT Number: NCT05678738

Acquiring and Targeting Heat Exposures Necessary for Action

The purpose of this research study is to better understand ways that women and men differ physiologically, cognitively, physically, and cellularly to better prescribe helpful interventions that will prevent injury and risk of conditions like exertional heat illnesses or heatstroke. The main questions this project aims to answer are:

1. What is the relative stress contributing to performance differences between women and men during intense exercise in extremely hot and humid environments in response to exertional heat stress? 2. What is the relative contribution of responses in adipose tissue, cardiovascular tissue, gut microbiota, and musculoskeletal tissue on heat tolerance in women (vs. men) to exertional heat stress? 3. What is the impact of adding an antioxidant juice consumption regime and will it assist in enhancing performance during an acute bout of exercise-heat stress before and after heat acclimation?

Subjects enrolled and approved for participation will perform:

1. a heat acclimation protocol which includes the completion of 5 days of prescribed exercise-heat exposure 2. two separate acute exercise-heat exposures for the assessment of thermotolerance and the investigation of potential enhancements in thermoregulatory performance that may occur after the completion of a 5-day heat acclimation protocol 3. a subset of subjects enrolled and approved for participation who opt in to antioxidant berry supplement consumption will either consume the active or placebo product throughout their participation.

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Key information

Conditions

Heat Intolerance Fatigue; Heat Heat Stress Heat Stress Disorders Wounds and Injuries

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Human Performance Laboratory at the University of Connecticut

Storrs, Connecticut, 06269, United States

Who can participate

Healthy volunteers accepted: Yes

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

Inclusion criteria

  • Participants will be healthy men and women, aged 18-50 years, who speak and read the English language fluently. This is required because some of the cognitive tests test grammatical reasoning and offer directional cues recorded as audio files in English. VO2max tests will provide evidence of level of aerobic fitness required to participate in this study. The investigators will use ≥45 ml·kg-1·min-1 for male participants, ≥40 ml·kg-1·min-1 for female participants as our threshold for inclusion.
  • The target composition of our subject sample is 50% men and 50% women.
  • No difficulties with vision, hearing, or ability to read a computer screen and operate a computer keyboard and mouse.

Exclusion criteria

  • unable to visit the laboratory on the required, consistent schedule and consecutive required days (Days 2 and 3, Days 12 and 13)
  • any contraindications to participating in exercise lasting 60-120 minutes daily during a period of 2 consecutive days, 5 days within an 8-day period, and 2 additional days (if subjects elect to participate in the entire study, all options), screening will include resting blood pressure to exclude pre-hypertensive or hypertensive participants (resting BP > 120 mmHg and 80mmHg systolic and diastolic, respectively)
  • any contraindications to exposure to exercise-heat stress (e.g., medications that affect thermoregulation, family or personal history of issues with anesthetics that indicate possible susceptibility to malignant hyperthermia, evidence of past heat intolerance)
  • tobacco use or electronic cigarettes (e-cigarettes) within the past 6 months
  • chronic illness (including diabetes, metabolic syndrome, thyroid disease, for example) or other chronic illnesses that make it unsafe for participants to participate in daily rigorous exercise in the heat
  • regular supplementation with blood thinners, including the use of aspirin
  • acute illness (e.g., influenza, head cold, gastrointestinal illness) during the week of scheduled testing
  • current positive COVID-test or infection and past COVID infection within past 6 months
  • contraindications to blood draw and if elected to be considered for participation with microdialysis and skeletal muscle biopsy procedures, contraindications to those individual procedures
  • for subjects who may not complete a DXA scan, history of claustrophobia
  • history of allergic reactions to medical tape and/or latex
  • currently participating in "non-traditional" diets including diets such as intermittent fasting, caloric restriction, highly limited consumption of large food classes (e.g., vegan)
  • consumption of antioxidant supplementation on a regular, long-term basis outside of the aronia supplementation regime for the study
  • limited decision-making ability
  • inability to participate in extended physical activity on a treadmill (i.e., standing, running, jogging, walking)
  • consumption of a non-traditional diet including diets such as intermittent fasting, caloric restriction, highly limited consumption of large food classes (e.g., vegan) (this includes individuals who are suffering with current diagnosed or undiagnosed eating disorder)
  • allergy to povidone, ethyl chloride, lidocaine, or bacitracin
  • pregnant or positive pregnancy test during DXA pre-procedures (see DXA SOP)
  • allergy to aronia berries, monkfruit, or sham juice ingredients

Treatment and study plan

Antioxidant Berry Supplementation

Dietary Supplement

Participants who opt-in will be instructed to consume 300mL of the bioactive (antioxidant berry) supplement every morning and afternoon during days of participation.

Acute and Chronic Exercise-Heat Stress

Other

All participants (male and female) will be exposed to repeated bouts of exercise-heat stress.

Placebo (non-juice) Supplementation

Dietary Supplement

Participants who opt-in will be instructed to consume 300mL of the placebo (non-juice) supplement every morning and afternoon during days of participation.

Primary outcomes

  1. Change in Rectal Temperature at Rest

    Time frame: Through study completion, an average of 14 days

    Rectal thermometer will be self-inserted by participants to assess core temperature prior to exercise-heat stress bouts

  2. Change in Rectal Temperature Rate of Rise

    Time frame: Through study completion, an average of 14 days

    Rectal thermometer will be self-inserted by participants to assess core temperature during exercise-heat stress bouts

  3. Change in Rectal Temperature at Thermal Threshold (38.5C)

    Time frame: Measured throughout 5 90-minute exercise-heat stress bouts (heat acclimation sessions)

    Rectal thermometer will be self-inserted by participants to assess core temperature during exercise-heat stress bouts at the thermal threshold of 38.5C

  4. Change in Mean Skin Temperature

    Time frame: Through study completion, an average of 14 days

    Prior to start of exercise, participants will be instrumented with iButton skin temperature sensors on the chest, shoulder, abdomen, neck, back, thigh, and calf

  5. Change in Heart Rate

    Time frame: Through study completion, an average of 14 days

    A heart rate monitor will be worn by participants throughout the exercise-heat stress bouts

  6. Change in Heart Rate at Thermal Threshold (38.5C)

    Time frame: Measured throughout 5 90-minute exercise-heat stress bouts (heat acclimation sessions)

    A heart rate monitor will be worn by participants throughout the exercise-heat stress bouts to assess HR at the thermal threshold of 38.5C

  7. Change in Whole Body Sweat Rate

    Time frame: Measured at the beginning and end of 5 90-minute exercise-heat stress bouts (heat acclimation sessions)

    Difference in body weight measurement measured prior to and at the cessation of each exercise-heat stress bout

  8. Change in Sweat Metabolite and Protein Expression

    Time frame: Measurement completed during each exercise-heat stress bout (Heat Tolerance Tests 1 [days 5 and 12] and 2 [days 6 and 13]) both before and immediately after heat acclimation as well as the final heat acclimation session (HA5 - day 11)

    Sweat samples will be collected and assessed for metabolite and protein expression discovery via mass spectrometry

  9. Change in Cognitive Measures - Visual Vigilance

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of visual vigilance through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  10. Change in Cognitive Measures - Psychomotor Vigilance

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of psychomotor vigilance through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  11. Change in Cognitive Measures - Four Choice Task

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of four choice task success through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  12. Change in Cognitive Measures - Match to Sample

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of match to sample success through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  13. Change in Cognitive Measures - Repeated Acquisition

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of repeated acquisition through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  14. Change in Cognitive Measures - Grammatical Reasoning

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of grammatical reasoning through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  15. Change in Cognitive Measures - Profile of Mood States

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of profile of mood states through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  16. Change in Cognitive Measures - Stroop Task

    Time frame: Measurement completed immediately after one exercise-heat stress bout (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participants will perform an assessment of stroop task success through a validated computer programming system. The test is part of a larger Testing battery which should take approximately 30 minutes for completion

  17. Change in Physical Performance - Anaerobic Performance

    Time frame: Measurements completed immediately after the cognitive battery performed during the Heat Tolerance Test 2 (days 6 and 13) both before and immediately after heat acclimation

    Participants will be assessed for anaerobic performance with the completion of a 400 meter sprint for time. This test is part of a larger physical performance battery test which should take approximately 30 minutes for completion

  18. Change in Physical Performance - Agility Performance

    Time frame: Measurements completed immediately after the cognitive battery performed during the Heat Tolerance Test 2 (days 6 and 13) both before and immediately after heat acclimation

    Participants will be assessed for anaerobic performance with the completion of a quick feet agility test. This test is part of a larger physical performance battery test which should take approximately 30 minutes for completion

  19. Change in Physical Performance - Upper Body Strength Performance

    Time frame: Measurements completed immediately after the cognitive battery performed during the Heat Tolerance Test 2 (days 6 and 13) both before and immediately after heat acclimation

    Participants will be assessed for upper body strength performance with the completion of a handgrip strength test. This test is part of a larger physical performance battery test which should take approximately 30 minutes for completion

  20. Change in Physical Performance - Lower Body Power Performance

    Time frame: Measurements completed immediately after the cognitive battery performed during the Heat Tolerance Test 2 (days 6 and 13) both before and immediately after heat acclimation

    Participants will be assessed for lower body power performance with the completion of a vertical jump test. This test is part of a larger physical performance battery test which should take approximately 30 minutes for completion

  21. Change in Physical Performance - Lower Body Kinematic Performance

    Time frame: Measurements completed immediately after the cognitive battery performed during the Heat Tolerance Test 2 (days 6 and 13) both before and immediately after heat acclimation

    Participants will be assessed for lower body kinematic performance with the completion of the Landing Error Scoring System (LESS) Test. This test is part of a larger physical performance battery test which should take approximately 30 minutes for completion

  22. Change in Physical Performance - Balance Performance

    Time frame: Measurements completed immediately after the cognitive battery performed during the Heat Tolerance Test 2 (days 6 and 13) both before and immediately after heat acclimation

    Participants will be assessed for balance performance with the completion of the Balance Error Scoring System (BESS) Test. This test is part of a larger physical performance battery test which should take approximately 30 minutes for completion

  23. Change in Musculoskeletal Gene and Protein Expression

    Time frame: Measurement completed after the performance of an exercise-heat stress bout and physical performance battery (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Musculoskeletal tissue samples will be collected for analysis via RNA-seq

  24. Change in Musculoskeletal Fiber-Typing

    Time frame: Measurement completed after the performance of an exercise-heat stress bout and physical performance battery (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Musculoskeletal tissue samples will be collected for fiber-type analysis via immunohistochemical procedures

  25. Change in Musculoskeletal Mitochondrial Function

    Time frame: Measurement completed after the performance of an exercise-heat stress bout and physical performance battery (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Musculoskeletal tissue samples will be collected for analysis of mitochondrial function

  26. Change in Subcutaneous Abdominal Tissue (SCAAT) Lipolysis Rate

    Time frame: Measurement completed after the performance of an exercise-heat stress bout and physical performance battery (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    SCAAT lipolysis rate (interstitial glycerol and ethanol output:input) will be collected and assessed for fat mobilization and subcutaneous adipose tissue blood flow during exercise-heat stress bouts

  27. Change in Resting Energy Expenditure and Macronutrient Oxidation

    Time frame: Measurement completed after the performance of an exercise-heat stress bout and physical performance battery (Heat Tolerance Test 2 - days 6 and 13) both before and immediately after heat acclimation

    Participant resting energy expenditure, fat oxidation, and carbohydrate oxidation will be assessed via indirect calorimetry for the measurement of respiratory quotient and respiratory exchange ratio

  28. Change in Circulatory Indicators of Lipid Metabolism - NEFAs

    Time frame: Throughout study completion, an average of 14 days

    Blood samples will be collected and assessed for the expression of lipid metabolism biomarker Non-Essential Fatty Acids (NEFAs)

  29. Change in Circulatory Indicators of Lipid Metabolism - Insulin

    Time frame: Throughout study completion, an average of 14 days

    Blood samples will be collected and assessed for the expression of lipid metabolism biomarker Insulin

  30. Change in Circulatory Indicators of Lipid Metabolism - IGF-1

    Time frame: Throughout study completion, an average of 14 days

    Blood samples will be collected and assessed for the expression of lipid metabolism biomarker Insulin Growth Factor-1 (IGF-1)

  31. Change in Circulatory Indicators of Stress - Epinephrine

    Time frame: Throughout study completion, an average of 14 days

    Blood samples will be collected and assessed for the expression of physiological stress biomarker Epinephrine

  32. Change in Circulatory Indicators of Stress - Norepinephrine

    Time frame: Throughout study completion, an average of 14 days

    Blood samples will be collected and assessed for the expression of physiological stress biomarker Norepinephrine

  33. Change in Circulatory Indicators of Stress - Cortisol

    Time frame: Throughout study completion, an average of 14 days

    Blood samples will be collected and assessed for the expression of physiological stress biomarker Cortisol

  34. Change in Circulatory RNA Content

    Time frame: Throughout study completion, an average of 14 days

    Blood samples will be collected and assessed for intracellular RNA content

  35. Change in Circulatory Indicators of Inflammation - IL-1B

    Time frame: Measurement completed during the completion of exercise-heat stress bouts (Heat Tolerance Tests 1 [days 5 and 12] and 2 [days 6 and 13]) both before and immediately after heat acclimation

    Blood samples will be collected and assessed for the expression of inflammatory biomarker IL-1B

  36. Change in Circulatory Indicators of Inflammation - TNF-a

    Time frame: Measurement completed during the completion of exercise-heat stress bouts (Heat Tolerance Tests 1 [days 5 and 12] and 2 [days 6 and 13]) both before and immediately after heat acclimation

    Blood samples will be collected and assessed for the expression of inflammatory biomarker TNF-a

  37. Change in Circulatory Indicators of Inflammation - IFN-gamma

    Time frame: Measurement completed during the completion of exercise-heat stress bouts (Heat Tolerance Tests 1 [days 5 and 12] and 2 [days 6 and 13]) both before and immediately after heat acclimation

    Blood samples will be collected and assessed for the expression of inflammatory biomarker IFN-gamma

  38. Change in Gut Microbiome Diversity

    Time frame: Measurement completed prior to the completion of an exercise-heat stress bout (Heat Tolerance Test 2) both before and after heat acclimation

    Stool samples will be collected and assessed for the impact of gut microbiome diversity on heat intolerance

  39. Change in Saliva Metabolite Expression

    Time frame: Measurement completed during each exercise-heat stress bout (Heat Tolerance Tests 1 and 2) both before and after heat acclimation as well as the final heat acclimation session (HA5)

    Saliva samples will be collected and assessed for metabolite expression

  40. Change in Thermal Sensation

    Time frame: Through study completion, an average of 14 days

    0-8 Scale (cold to hot) that indicated how cold or hot the participant feels. 0 = extremely cold, 8 = extremely hot

  41. Change in Recovery

    Time frame: Throughout study completion, an average of 14 days

    Participants will be provided a WHOOP strap after the completion of their baseline visit and will be instructed on how to download the associated application and use of the device. The WHOOP device will be used to provide data on sleep quality and quantity, strain, and recovery

Secondary outcomes

  1. Change in Perception of Fatigue

    Time frame: Throughout study completion, an average of 14 days

    0-10 (no fatigue to extreme fatigue), scale indicates how fatigued the participant feels. High score indicates more fatigue (negative outcome)

  2. Change in Perception of Thirst

    Time frame: Throughout study completion, an average of 14 days

    0-9 (no thirst to extreme thirst), scale that indicates how thirsty the subject feels, a higher score is considered a negative outcome (more thirsty)

  3. Change in Environmental Perception

    Time frame: Throughout study completion, an average of 14 days

    Scale to assess participant perception of the environmental conditions, measurement scale identified as the modified environmental symptoms questionnaire (ESQ) which includes a minimum scale of "Not at all" and a maximum scale of "Extreme". Outcomes are considered worse when associated with greater extremes in documented answers

  4. Change in Rating of Perceived Exertion

    Time frame: Throughout study completion, an average of 14 days

    6-20 scale to assess participant perceived exertion levels (how hard they are working) during exercise-heat stress bouts. A greater score indicates greater levels of exertion.

  5. Change in Sleep Quality

    Time frame: Throughout study completion, an average of 14 days

    Scale to assess participant sleep habits including quantity and quality, measurement scale identified as the Kalinska sleep diary (KSD) which is a 9-point scale with increasing severity from 1 (extremely alert) to 9 (extremely sleepy - fighting sleep)

  6. Change in Body Mass

    Time frame: Throughout study completion, an average of 14 days

    Participants will have nude body weight (kg) assessed at the beginning and end of each testing session

  7. Change in Reproductive Hormone State - Estradiol

    Time frame: Throughout study completion, an average of 14 days

    Blood plasma samples will be collected for the measurement of circulating estradiol

  8. Change in Reproductive Hormone State - Progesterone

    Time frame: Throughout study completion, an average of 14 days

    Blood plasma samples will be collected for the measurement of circulating progesterone

  9. Change in Reproductive Hormone State - Testosterone

    Time frame: Throughout study completion, an average of 14 days

    Blood plasma samples will be collected for the measurement of circulating testosterone

  10. Change in Reproductive Hormone State - LH

    Time frame: Throughout study completion, an average of 14 days

    Blood plasma samples will be collected for the measurement of circulating luteinizing hormone (LH)

  11. Change in Reproductive Hormone State - FSH

    Time frame: Throughout study completion, an average of 14 days

    Blood plasma samples will be collected for the measurement of circulating follicle stimulating hormone (FSH)

  12. Change in Cardiovascular Response - Blood Pressure

    Time frame: Throughout study completion, an average of 14 days

    Blood pressure will be measured manually prior to each testing session with the documentation of systolic and diastolic measurements

Sponsors and collaborators

Lead sponsor

University of Connecticut

Other

Collaborators

  • United States Department of Defense

Registry information

Official study title

Enhancing Lethality by Targeting Cognitive and Physiological Mechanisms of Female Warfighter Resiliency to Consecutive Days of Intense Exercise in the Heat

Acronym: ATHENA

Important dates

Study start
2021
Primary completion
2024
Study completion
2024
First posted
Jan 10, 2023
Registry last updated
Sep 11, 2025

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.

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