Predicted sweat rate in fluctuating thermal conditions

Area of Science:

• Environmental Physiology
• Occupational Health
• Thermal Stress Assessment

Background:

• The ISO 7933 standard's Required Sweat Rate Index is unsuitable for dynamic thermal environments.
• Time-weighted averages underestimate physiological strain in hot conditions due to non-linear stress-strain relationships.

Purpose of the Study:

• To develop and validate a simple algorithm for predicting sweat rate under fluctuating thermal exposures.
• To account for the exponential averaging response of mean skin temperature and sweat rate.

Main Methods:

• Derived a simple algorithm incorporating exponential averaging based on time constants.
• Time constants used: 3 min for mean skin temperature, 25 min and 10 min for sweat rate.
• Validated the model using independent experimental data.

Main Results:

• The algorithm predicts sweat rate considering past thermal exposure.
• Achieved a correlation coefficient of 0.780 between observed and predicted sweat rates.
• Highlighted the importance of exponential averaging due to significant individual differences and data variability.

Conclusions:

• The proposed algorithm offers a more accurate method for sweat rate prediction in fluctuating heat.
• Exponential averaging is crucial for precise physiological strain assessment in dynamic environments.
• The model's performance underscores the need to consider individual variability in thermal responses.