A wearable real-time activity tracker

Abstract

Exercise and physical activity is a driving force for mental health. Major challenges in the treatment of psychological diseases are accurate activity profiles and the adherence to exercise intervention programs. We present the development and validation of CHRONACT, a wearable realtime activity tracker based on inertial sensor data to support mental health. CHRONACT comprised a Human Activity Recognition (HAR) algorithm that determined activity levels based on their Metabolic Equivalent of Task (MET) with sensors on ankle and wrist. Special emphasis was put on wearability, real-time data analysis and runtime to be able to use the system as augmented feedback device. For the development, data of 47 healthy subjects performing clinical intervention program activities were collected to train different classification models. The most suitable model according to the accuracy and processing power tradeoff was selected for an embedded implementation on CHRONACT. A validation trial (six subjects, 6 h of data) showed the accuracy of the system with a classification rate of 85.6%. The main source of error was identified in acyclic activities that contained activity bouts of neighboring classes. The runtime of the system was more than 7 days and continuous result logging was available for 39 h. In future applications, the CHRONACT system can be used to create accurate and unobtrusive patient activity profiles. Furthermore, the system is ready to assess the effects of individual augmented feedback for exercise adherence.