Synchronicity: A Measure of Multi-Joint Movement Coordination in Device Assessment.

This work explores the concept of movement coordination over time; smooth multi-joint gestures are a hallmark of healthy and normative body function. Deviations from normative movement coordination are linked to various health conditions, such as stroke or injury, and can lead to further complications if not addressed. Identifying abnormal movement and quantifying its degree is therefore crucial. Although some quantitative assessments exist, final evaluations often require expert input from occupational or physical therapists. We investigate the characterization of joint movements using motion capture as an objective indicator of synchronous behavior and propose a new quantitative metric to assess device and rehabilitation interventions, synchronicity. We apply our metric to three studies with various populations that compare normative hand use to movement with wrist braces, transradial prostheses, and a wrist exoskeleton, revealing that synchronicity may be an indicator of device embodiment and function.