Evaluation of an Activity Monitor for the Objective Measurement of Free-Living Physical Activity in Children With Cerebral Palsy

Abstract Objective To explore the use of an activity monitor (AM) to objectively characterize free-living physical activity (F-LPA) in children with mobility impairment resulting from cerebral palsy (CP). Design First, a validation study compared outcomes from the AM with video evidence. Second, multiday F-LPA was characterized. Relationships between laboratory measures and F-LPA were explored. Setting The evaluation study was conducted in a laboratory environment. F-LPA monitoring was conducted in the participants' free-living environment. Participants Convenience sample of ambulatory children (N=15; 11 boys, 4 girls) aged 5 to 17 years with CP undergoing gait analysis. Interventions Not applicable. Main Outcome Measures Accuracy of the AM for sitting/lying time, upright time, stepping time, and strides taken. Daily volumes of F-LPA of children with CP. Results AM outcomes in comparison with video-based analysis were (mean ± SD) 97.4%±2.7%, 101.1%±1.5%, 99.5%±6.6%, 105.6%±15.8%, and 103.8%±10.1% for sitting/lying time, upright time, standing time, stepping time, and stride count, respectively. Participants' daily F-LPA demonstrated considerable variation: mean standing time ± SD, 2.33±.96h/d; mean stepping time ± SD, 1.68±.86h/d; mean steps per day ± SD, 8477±4528; and mean sit-to-stand transitions per day ± SD, 76±49. Laboratory-measured cadence and mobility level were related to F-LPA, but not directly. Conclusions The AM demonstrated excellent ability to determine sitting/lying and upright times in children with CP. Stepping time and stride count had lower levels of agreement with video-based analysis but were comparable to findings in previous studies. Crouch gait and toe walking had an adverse effect on outcomes. The F-LPA data provided additional information on children's performance not related to laboratory measures, demonstrating the added value of using this objective measurement technique.