Uswatte G, Giuliani C, Winstein C, Zeringue A, Hobbs L, Wolf SL. Validity of accelerometry for monitoring real-world arm activity in patients with subacute stroke: evidence from the Extremity Constraint-Induced Therapy Evaluation trial. Objective: To examine the psychometric properties of an objective method for assessing real-world arm activity in a large sample with subacute stroke. Design: Validation study. Setting: Community. Participants: Persons 3 to 9 months poststroke (N=169) with mild to moderate motor impairment of their hemiparetic arm enrolled in a multisite, randomized clinical trial of constraint-induced movement therapy. Interventions: Not applicable. Main Outcome Measures: Participants wore an accelerometer on each arm outside the laboratory for 3 days before and after treatment or an equivalent no-treatment period. They also completed the Actual Amount of Use Test (AAUT), which is an observational measure of spontaneous more-impaired arm use, and the Motor Activity Log (MAL), which is an interview assessing more-impaired arm use in daily life. Results: Low-pass-filtered accelerometer recordings were reliable (r range, >.8) and stable (P range, >.48). Their validity was also supported. Correlations calculated across all participants at baseline between the ratio of more-impaired to less-impaired arm accelerometer recordings and AAUT and MAL scores were .60 and .52, respectively. Conclusions: Accelerometry provides an objective, real-world index of more-impaired arm activity with good psychometric properties. © 2006 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.