How Many Hours of Device Wear Time Are Required to Accurately Measure Physical Activity Post Stroke?

Background. Inadequate physical activity participation is a risk factor for secondary stroke. Before implementing appropriate management strategies, we need to accurately measure the physical activity of stroke survivors. We aimed to determine the duration of physical activity monitoring post-stroke that constitutes a valid day. Methods. We sampled stroke survivors’ physical activity for one week following discharge from inpatient rehabilitation using the Sensewear Armband (Bodymedia, Pittsburgh, PA, USA). To determine the impact of total daily wear time on activity estimate (sedentary, light, and moderate to vigorous physical activity) accuracy, we performed simulations, removing one, two, three, or four hours from a 14-h reference day, and analysed them with linear mixed models. Results. Sixty-nine participants (46 male, 65 ± 15 years) with 271 days of physical activity data were included. All physical activity variables were significantly underestimated for all data sets (10, 11, 12, or 13 h) compared to the 14-h reference data set. The number of days classified as not meeting physical activity recommendations increased as daily monitoring duration decreased: 13% misclassification with 10-h compared to 14-h dataset (p = 0.011). Conclusions. The accuracy of physical activity estimates increases with longer daily monitoring periods following stroke, and researchers should aim to monitor post-stroke physical activity for 14 daytime hours.