To the Editor Wiebe et al1 examined the relationships between physical activity and symptoms of patients following concussion. We have several methodological concerns.
First, this study used accelerometer-based step count to reflect physical activity level of patients. The validity of accelerometer-based step count has been questioned. For example, a particular model of accelerometer overestimated step count by 5265 steps per day in free-living condition.2 However, the model of accelerometer used in this study was not reported nor was the compliance rate (eg, mean wear/nonwear time per day), which may affect the validity of measurement.
Lee KY, Lam MHS, Deng Y. Measuring Postconcussive Activity Levels of Patients: Step Count or Activity Intensity? JAMA Pediatr. 2017;171(5):493–494. doi:10.1001/jamapediatrics.2017.0131
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