Validation of a Simple Metabolic-Equivalent-of-Task Sensor Based on a Low-Cost NFC RFID Wristband

In this paper, a simple solution allowing continuous actimetry with an uniaxial magnetometer is presented. Worn on the wrist to monitor the forearm tilt, it can estimate the instantaneous metabolic-equivalent-of-task during physical activity. Autonomous acquisition and data transfer are managed by a radio frequency identification chip supporting the near field communication (NFC) standard. Thus, the solution can transfer measurements to an NFC-enabled device (computer and smartphone) that runs a custom algorithm. The algorithm output signal was indirectly calibrated to an accurate calorimetry device to display the real energy expenditure of the user during the physical activity session.