BackgroundDuring strenuous exercise, individuals face a significant risk of developing heat-related illnesses, such as exertional heatstroke (EHS). Parameters that have demonstrated an important role in monitoring and prevention of EHS development include heart rate (HR), hydration status (determined by serum electrolyte concentrations), and core body temperature. In this study, the performance of two integrated HR monitor and pulse oximeter modules (AFE4403 from Texas Instruments and MAXIM30101 from Maxim Integrated) in capturing raw photoplethysmography (PPG) signals was evaluated during resting, exercise, and motion. ResultsPPG signals collected from a wrist-worn device using green light-emitting diodes (LED) provided good HR estimates. However, the device was not resistant to motion artefacts. ConclusionFurther work was conducted to fabricate sensors that could measure sodium concentrations in sweat, and core body temperature from the skin. Once each sensor prototype is finalised, sensor integration could result in a device that measures three bodily parameters to a sufficient degree of accuracy in order th predict the onset of EHS. The fabrication of the other two sensors has not been described in this report.