More Than Just Arm Movement: Finger-Worn Accelerometers Provide a Valid and Sensitive Alternative to Wrist-Worn Accelerometers for Measuring Real-World Upper-Limb Performance in Stroke Survivors

Objective To investigate the clinical validity of finger-worn accelerometers for providing a comprehensive assessment of upper-limb motor performance in individuals post-stroke in real-world environments, compared to wrist-worn accelerometers, and to examine how the clinimetric properties of wearable-based motor performance measures vary with the duration of patient data collection. Design Cross-sectional observational design. Setting Research laboratory and free-living environments. Participants Twenty-seven participants aged 18-80 years with ischemic or hemorrhagic stroke at least six months prior to enrollment and mild-to-moderate upper-limb impairment without severe range-of-motion restrictions were enrolled. Three participants were ineligible and four withdrew, resulting in a final cohort of 20 participants (N = 20). Interventions Not applicable. Main Outcome Measures Wearable-based motor performance measures derived from fine-hand movements, gross-arm movements, and the combination of fine-hand and gross-arm movements captured by finger-worn and wrist-worn accelerometers in naturalistic settings for 6.4 ± 1.8 days. Results Wearable-based motor performance measures from fine-hand movements demonstrated the strongest convergent validity with standardized clinical assessments of motor capacity and performance—including the Fugl-Meyer Assessment for Upper Extremity (FMA-UE), Wolf Motor Function Test (WMFT), and Motor Activity Log (MAL)—as well as the strongest known-group validity in distinguishing impairment levels and the highest test-retest reliability, followed by measures from combined and gross-arm movements. Convergent validity and test-retest reliability improved with longer monitoring durations, with four days being sufficient to obtain accurate and reliable upper-limb measures. Conclusions Wearable-based motor performance measures from finger-worn accelerometers provide a more comprehensive assessment of upper-limb motor performance than those from wrist-worn accelerometers, supporting their use for real-world monitoring in individuals post-stroke. Furthermore, the improvements in clinimetric properties of wearable-based motor performance measures with longer monitoring durations highlight the importance of multi-day monitoring to mitigate day-to-day variability and ensure robust assessment.