Development and Pilot Evaluation of the ArmTracker: A Wearable System to Monitor Arm Kinematics During Daily Life

sensing technology is proving useful for promoting health and fitness for the general public and athletes, yet few devices are tailored to people with movement impairments. For devices targeting home-based rehabilitation, it is crucial to have robust and non-obtrusive sensors capable of measuring activity for long periods of time outside of a laboratory environment. Studies focusing on continuous monitoring of arm activity during daily life over weeks or months only use IMU sensors or accelerometers at the wrist, and do not capture multi-segment kinematics. In this paper we present the development of the ArmTracker, a fully portable, non-obtrusive and wearable IMU-based motion capture system that can measure arm and torso kinematics for long-periods of time during daily life. We also present the results of a preliminary evaluation of the prototype, carried out with an unimpaired subject and a subject with Becker muscular dystrophy (BMD). Both subjects were asked to wear the ArmTracker device during daily life for 7 hours. We carried out an exploratory graphical analysis with the measured data using three types of movement quality metrics: 1) Range of Motion, 2) Functional Workspace Distribution and, 3) Accelerometry. Results provided an insightful view on the motor function capabilities and limitations of the two subjects. Arm activity of the subject with BMD showed low variability in terms of joint angles and hand positions over the workspace with a clear preference of using his hands in front and below shoulder height. Arm movements of the BMD subject were also slower compared with the unimpaired subject and with a slight preference for using the dominant arm. We plan to extend this study with a larger sample of subjects, and with measurements over several days and weeks to capture representative data on arm activity.