Measuring Postconcussive Activity Levels of Patients: Step Count or Activity Intensity?

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.