Comparison of Reachable Workspace Capacity to Real-World Arm Use Performance: A Wearable Accelerometry Study on Chronic Stroke

Abstract

Highlights What are the main findings? Reduced Reachable Workspace (RWS), quantified using the camera-derived Relative Surface Area (RSA) score, was associated with decreased arm use in daily life (ρ = 0.66), as measured with an accelerometer-based, smartwatch-derived metric in 14 individuals with chronic stroke. RSA was also significantly associated with the Box and Block Test (BBT), Upper-Extremity Fugl-Meyer Assessment (UEFM), and Motor Activity Log (MAL), with correlation strengths ranging from ρ = 0.57 to 0.76. What are the implications of the main findings? Combining camera-based RWS assessment with smartwatch monitoring may help relate upper-extremity movement capacity measured in the clinic to arm movement behavior during daily life. RSA may provide an objective and spatially detailed measure of post-stroke arm impairment that can be interpreted alongside clinical motor assessments and patient-reported arm use. Abstract Reachable workspace (RWS) quantifies the three-dimensional space accessible to the upper limb, but its relationship with real-world arm use after stroke remains unclear. This study examined associations between camera-based RWS and smartwatch-derived movement behavior in 14 individuals with chronic stroke. Relative surface area (RSA) was measured at baseline, after which participants wore a smartwatch on the affected arm. Smartwatch data were summarized using Gross Movement and Activity Count (GMAC), representing the proportion of wear time spent in active arm movement within a functional workspace, and Active and Diverse Exploratory Movement (ADEM), representing the proportion of wear time that was active and diverse. Clinical outcomes included the Box and Block Test (BBT), Upper-Extremity Fugl-Meyer Assessment (UEFM), and Motor Activity Log (MAL). Total RSA and several workspace regions were reduced in the paretic compared with the nonparetic limb. Greater total RSA was significantly associated with ADEM (ρ = 0.66, p = 0.01), while its association with GMAC was numerically weaker and non-significant (ρ = 0.47, p = 0.09). RSA was also significantly associated with BBT, UEFM, and MAL, with correlations ranging from ρ = 0.57 to 0.76. These findings link camera-based RWS with wrist-worn measures of real-world arm performance after stroke.