Non-invasive Prediction of Thermal Strain in Healthy Male Adults

Study Overview
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Brief Summary
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This is primarily an experimental study investigating methods of temperature measurement / heat strain detection. In the calibration study, there are different skin temperature sensor types, and in the prediction study there are different methods for determining heat strain, including conventional methods (rectal, gastro-intestinal), the development of a prediction model, and an index based on heart rate variability.

Official Title
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Single-centre Experimental Evaluation of Methods for Reliable Non-invasive Prediction of Thermal Strain in Healthy Male Adults

Conditions
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Heat Stress

Intervention / Treatment
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* Other: Heat strain


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Apparently healthy males aged 18-45 y regularly participate in sport, exercise, or equivalent physical activity on a weekly basis. Exclusion Criteria: Known injuries or illnesses that may affect safe participation. These include injuries or illnesses involving (but not limited to): cardiovascular, renal, or gastrointestinal tract heat or exercise intolerance acute infections, immunological diseases (including asthma) psychiatric disorders. Participants must not be currently or previously on cardiovascular-related medication and must not be taking psychotropic medication (last 60 days).

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Male

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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Design Details

Primary Purpose: Screening
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High heat strain<br>participants exercised at 75% of their heart rate maximum (HR max) and wore light athletic clothing (t-shirt and shorts) | Other: Heat strain<br>* The experimental procedure comprised 15 min baseline seated rest (23.2 ± 0.3°C, 24.5 ± 1.6% relative humidity), followed by 15 min seated rest and cycling in a climatic chamber (35.4 ± 0.2◦C, 56.5 ± 3.9% relative humidity; to +1.5◦C or maximally 38.5°C rectal temperature, duration 20-60 min), with a final 30 min seated rest outside the chamber.<br>|
| Experimental: Low heat strain<br>participants exercised at 50% HR max, wearing protective firefighter clothing (jacket and trousers) | Other: Heat strain<br>* The experimental procedure comprised 15 min baseline seated rest (23.2 ± 0.3°C, 24.5 ± 1.6% relative humidity), followed by 15 min seated rest and cycling in a climatic chamber (35.4 ± 0.2◦C, 56.5 ± 3.9% relative humidity; to +1.5◦C or maximally 38.5°C rectal temperature, duration 20-60 min), with a final 30 min seated rest outside the chamber.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Core body temperature | Rectal core body temperature (unit of measure is degree celsius °C) | 90 minutes | 
| Predicted core body temperature | Estimated core body temperature (°C) from selected non-invasive measurements: applying a multiple linear regression model several predictive parameters, including skin temperature at different body sites, heat flux at different body sites, and heart rate will be combined to achieve one reported temperature value (°C) | 90 minutes | 
| ECG-based heat strain index | ECG-based index of heat strain derived from heart rate variability | 90 minutes |