Wearable Inertial and Bio-signal Device for Real-time Swimmer's Monitoring

There is a growing interest on wearable devices to monitor health during sport activities. These devices may be used only for monitoring purposes or allow coaches to evaluate the athlete's biological signals and physical performance. In many sports, the acquired data is available for the user, but also can be monitored in real time by the technical staff, by using some type of communication. Nevertheless, in sports like swimming commonly the acquired data is stored in the portable device and analyzed only after the training session, due to the transmission issues related to the harsh environment of the pool. In this paper we propose a novel system that allows the technical staff to monitor and analyze the swimmer's inertial (AHRS) and bio-signals (heart rate and pulse oximetry) in real time. To this aim, two radiofrequency communications systems were used, one at 5.3kHz for the heart rate sensor and another at 433MHz to communicate with the base station outside the swimming pool. This communication has been tested successfully for all swimming styles, turns and at various deep levels in the underwater phase. Additionally, a computational application shows, in real time, the sensors information, as well as few additional information processed using machine learning algorithms, like swimming style, turns, average speed and stroke counting. Unlike the common systems, the proposed device effectively yields immediate feedback to the swimmers based on the real time data analysis, which can be given by the coach or automatically by a haptic actuator in the wearable device.