Multi-Task Classification of Physical Activity and Acute Psychological Stress from Wearable Device Data^*

Acute psychological stress (APS) is a complex multifactorial event caused by drivers such as anxiety, mental and competition stress. It can occur concurrently with physical activity (PA), making its detection and classification challenging. This study investigates the detection and classification of APS (alone or concurrent with PA) by using physiological signals collected using Empatica E4 wristband. Multi-task Extreme Gradient Boosting (XGBoost) achieved F1 scores of 99.89% and 98.31% for the classification of various PA (treadmill run, stationary bike) and APS (competitive mental, anxiety stress, non-stress) and sedentary state. Shapley additive explanations (SHAP) is used to interpret the global importance of the physiological signals, determining the order of importance physiological signals for APS detection and classification. The results indicate (in decreasing order of importance): galvanic skin response (GSR), heart rate (HR), skin temperature (ST), accelerometer (ACC) X-axis, ACC Y-axis, ACC Z-axis. The increase in GSR and HR are positively correlated with the occurrence of APS as indicated by high positive SHAP values.