LAUSR

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. Second,stepcountmaynotsufficientlyreflectthetruephysical activity level of patients following concussion. Patients with concussion may have fewer walking-based activities (1815 steps per day as reported in this study), and their physical activity may have been restricted to low-intensity, home-based, multidimensional body movements. In this connection, using an accelerometer to capture multidimensional body movements and express these as “activity intensity” would better reflect the true physical activity level. However, “activity intensity” was not reported in this study, despite using an accelerometer. Third, the patients were aged 11 to 19 years and were adolescents and young adults. The body of evidence shows that the physical activity level of adolescents and adults are different.3 The recovery rate following concussion in adolescents and adults is also different.4 Therefore, it calls into question whether it is appropriate to include both adolescents and adults in the data analyses.