Heart Rate, Skin Temperature and Skin Humidity and their Relationship to Accumulated Fatigue

Accumulated fatigue and physical stress could negatively affect performance and health of the individual. Without adequate rest and recovery, it could lead to injuries especially for the professions where prolonged exposure to and physical exertion in high temperatures are required. In this study, we focus on physiological indicators related to accumulated fatigue and heat stress. Common physiological responses to heat stress are changes in heart rate, core body temperature and sweating rate. The objective of this study is to monitor the heart rate, skin temperature and skin humidity of the new recruited soldiers during the last week of multiple weeks training period in high temperature where accumulated fatigue is expected. The measurements are collected during their sleep. Experimental results show an increasing trend of the average resting heart rate in multiple participants. There is an increasing trend of skin temperature in one participant, the data also show consistently high skin humidity for this participant. However, there are two participants with decreasing trend of skin temperature. Average skin humidity measurements are mostly stable for all of the participants. Overall, the experiment results show that resting heart rate could be an indicator of the accumulated fatigue or heat stress while there is no consistent trend on the skin temperature and skin humidity. However, more experiments are required in order to establish relationship between heart rate, skin temperature or skin humidity and accumulated fatigue.