Measuring Physical Activity in Spinal Cord Injury Using Wrist-Worn Accelerometers

Abstract

Abstract OBJECTIVE. Our objective was to evaluate interunit agreement and construct validity of two activity monitors (Actiwatch Score and PRO-Diary) in people with and without spinal cord injury. METHOD. Thirty-eight participants (19 with spinal cord injury; 19 age- and sex-matched controls; mean age = 49 yr) wore both monitors and completed tasks during one visit ranging in physical intensity. To compare activity by group and monitor, we conducted t tests. We assessed interunit agreement using intraclass correlations and Bland–Altman plots. RESULTS. Both monitors demonstrated significantly different increasing physical activity levels with higher intensity tasks. Participants with spinal cord injury had similar activity counts within tasks compared with controls except for walking–wheeling. Agreement was high between monitors across tasks (interclass correlation coefficients = .78–.97). CONCLUSION. Both monitors demonstrated good construct validity for measuring physical activity across activities and high agreement. Either monitor is appropriate to examine physical activity patterns in people with spinal cord injury.