Assessing Non-Intrusive Wearable Devices for Tracking Core Body Temperature in Hot Working Conditions

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Heat-related illness is a growing concern for workers in temperate climates as rising temperatures and heatwaves put them at risk of exertional heat stroke. Monitoring biometrics that predict heat stroke, such as core temperature, is increasingly important. To monitor biometrics, wearable sensing technologies have been proposed as an alternative to the ingestible telemetric pill. However, limited studies have validated the accuracy of these sensors in different temperature conditions. Therefore, this study aims to assess the validity of wearable devices placed on different areas of the body for measuring core body temperature (CT) during repetitive physical activity in high temperature conditions. Ten male participants performed dumbbell curling exercises at 33 °C and roughly 50% relative humidity, and data from the pill (the criterion standard) were compared to data from two wearable sensors–Slate Safety and Zephyr. Results showed that Slate Safety [Bias (Precision) = 0.20 (0.35) °C) and Zephyr [Bias (Precision) = −0.03 (0.35) °C] recorded bias and precision within acceptable limits. The correlation analysis showed that wearable sensors are suitable for real-time monitoring of an individual’s level of heat stress in high temperatures. However, there was a proportional bias with these CT measuring devices, meaning that the reported temperature values are consistently deviated from the true values. The results of this study contribute to the ongoing discussion of the most appropriate methods for monitoring heat stress and provide valuable information for practitioners working in this field.