Evaluation of an activity monitor for the objective measurement of free-living physical activity in children with cerebral palsy

Intervention in children with mobility limitation due to cerebral palsy (CP) is often aimed at enhancing mobility. An outcome measure of such intervention should, therefore, be free-living physical activity (F-LPA). This study explored the use of an objective measurement tool, the activPAL activity monitor (AM), in characterising F-LPA in children with CP. A validation study in a laboratory environment comparing AM outcomes with video evidence was followed by a multiday characterisation of F-LPA. Relationships between laboratory measures and F-LPA were explored. A convenience sample of 15 (11M, 4F) ambulatory children (5-17 years) with the condition of CP was studied. AM outcomes in comparison to video based analysis were 97.4% (SD=2.7), 101.1% (SD=1.5), 99.5% (SD=6.6), 105.6% (SD=15.8) and 103.8% (SD=10.1) for sitting/lying time, upright time, standing time, stepping time and stride count respectively. Participants’ daily F-LPA demonstrated considerable variation: Standing time 2.33 (SD=0.96) hours/day, stepping time 1.68 (SD=0.86) hours/day, steps 8477 (SD=4528) per day and 76 (SD=49) sit to stand transitions per day. Laboratory measured cadence and Gillette Functional Assessment Questionnaire score were related to F-LPA, but not directly. 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 with 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.