Validity of the Apple Watch(R) for monitoring push counts in people using manual wheelchairs

Description

<p> Objective: A recent Apple Watch ^® activity-monitoring innovation permits manual wheelchair users to monitor daily push counts. This study evaluated the validity of the Apple Watch ^® push count estimate. <br/></p><p>Design: Criterion validity. Setting: Southern Finland and Southeast Queensland, Australia. Participants: Twenty-six manual wheelchair users from Finland and Australia were filmed completing a standardized battery of activities while wearing the Apple Watch ^® (dominant wrist). Outcome Measures: Wheelchair pushes as determined by the Apple Watch ^® were compared to directly observed pushes. <br/></p><p>Results: Agreement between Apple Watch ^® push counts and directly observed pushes was evaluated using Intraclass correlation coefficients (ICC), Pearson correlations and Bland-Altman analyses. Apple Watch ^® pushes and directly observed push counts were strongly correlated (ICC = 0.77, P < 0.01) (r = 0.84, P < 0.01). Bland Altman plots indicated that the Apple Watch ^® underestimated push counts (M = −103; 95% ULoA = 217; LLoA = −423 pushes). Mean absolute percentage error was 13.5% which is comparable to studies evaluating agreement between pedometer-based step counts and directly observed steps.</p><p>Conclusion: Apple Watch ^® push-count estimates are acceptable for personal, self-monitoring purposes and for research entailing group-level analyses, but less acceptable where accurate push-count measures for an individual is required. </p>