The Detection of Heat Stress by Assessing Individual Body Responses to Heat (Heat Strain) in Young and Healthy Non-athlete Participants

Study Overview
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Brief Summary
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• This study investigates and compares the within and in-between variances of the body responses to different heat stressors in a controlled lab-setting. The participants will be exposed to different heat sources while a variety of physiological heat strain reactions such as heartrate, sweat rate, and core body temperature are recorded using on- and in-body devices. For the participant monitoring during the study, medical grade devices such as a certified ECG and a swallowable sensor-pill to continuously monitor the core body temperature will be applied. A one-for-all wearable device is additionally applied for physiological validation. Further, sweat will be collected to assess (i) the local sweat rate and (ii) the appearance of different heat stress associated molecular markers in this non-invasively collectable biofluid. As a secondary aim, a model will be developed that will enable to predict the different heat stress sources out of the heat strain measurements.

Official Title
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HEAT Stress Detection From Personally STandARdized Heat Strain Measurements - The HEATSTAR Pilot Trial

Conditions
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Heat Stress

Intervention / Treatment
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* Other: Elevated ambient heat
* Other: Elevated relative humidity
* Other: Exertion


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy participant, able to give consent Age 18-40 years Non-athlete (<4h sport/week) BMI<30 (non-obese) German speaking, or fluent in German Exclusion Criteria: Pregnancy (urine pregnancy test), and breastfeeding Regular medication intake (excluding birth control pill) Intake of drugs and/or daily alcohol consumption Fever or symptoms of an acute infection (cough, shortness of breath, sore throat, taste loss) Active smoking or history of smoking <9 months ago Mobility impairment Traveled (<1 month ago) to a warm/hot temperature zone and stayed for >6 days Any chronic conditions such as: high blood pressure, diabetes mellitus, immuno-deficiencies, sweat disorders such as anhidrosis Color blindness (STROOP test) Weight <40 kg (e-Celsius pill) Diverticulum or obstructions of the gastrointestinal tract (including motility disorders, swallowing disorders) as well as major abdominal surgery (e-Celsius pill) Need of exposure to strong electromagnetic fields during study participation, above all MRI examinations (e-Celsius pill)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Healthy participants<br>Age of the participants is between 18-40 years, females and males equally distributed | Other: Elevated ambient heat<br>* Temporary exposure to increased ambient temperature +10°C (the effect of the intervention is fully and spontaneously reversible)<br>Other: Elevated relative humidity<br>* Temporary exposure to increased ambient relative humidity +40% (max. 90%) (the effect of the intervention is fully and spontaneously reversible)<br>Other: Exertion<br>* Temporary exertion on an ergometer (1W/kg body weight) (the effect of the intervention is fully and spontaneously reversible)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The within and between subject heat strain marker variability in relation to specific heat stress sources (ambient heat, ambient humidity, exertion, and clothing) | The primary endpoint is the within- and between- subject heat strain marker variability of HR, CBT, WSR, and LSR in relation to various heat stress sources (increased ambient temperature, increased relative humidity, and exertion, all without and with additional clothing. | Max. 7 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Accuracy to detect the specific heat stress source (such as ambient heat, relative humidity) from different on- and in-body measurements | The models for the primary endpoints will be extended to explore the relationships between heat strain parameters, heat stress sources, as well as personal characteristics. Additionally, prediction of heat stress source will be explored. | Max. 7 days | 
| Assessment of short-term heart rate variability in context to each heat stressor. | Short-term HRV with a repeating time frame of 5min. Root mean square of successive RR interval (RMSSD; in [ms]) and the Standard-deviation of RR intervals (SDRR; in [ms]) will be computed with respect to each heat stress source. | Max. 7 days | 
| Temperature [°C] and relative humidity [%] of the microenvironment as an additional source of information for patterns to detect heat stressors | Features of temperature [°C] and relative humidity [%] of the microenvironment as additional model predictors. | Max. 7 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Heat Strain, Wearable, Sweat Analysis