Ambulatory activity patterns in cerebral palsy with the StepWatch TM

Ambulatory activity patterns in cerebral palsy with the StepWatch TM
KF BJORNSON PHD PT 1, K SONG MD 2, C ZHOU PHD 3, K COLEMAN MS 4
1 Development Medicine, Seattle Children’s Research Institute, University of Washington, Seattle, WA;
2 Orthopedics, Seattle Children’s, University of Washington, Seattle, WA;
3 Biostatics, Seattle Childrens, University of Washington, Seattle, WA;
4 Clinical Research, OrthoCare Innovations, Seattle, WA, USA

Background/Objectives: StepWatch (SW) accelerometry data describes walking activity with the numeric variables of strides/day, % time active and peak strides/durations of time. Ambulatory activity curves allow interpretation of these variables in a combined format. The purpose of this study is to characterize community based daily ambulatory activity patterns in cerebral palsy as compared to non-impaired youth.
Design: Cross-sectional comparison cohort.
Participants and Setting: Eighty-one children with CP, gross motor function classification system [GMFCS] levels I [n=31], II [n=30] and III [n=20]; seen for care at three regional pediatric specialty care hospitals and 204 youth developing typically (YDT), all ages 10-13 years.
Materials/Methods: Participants wore the SW on their lateral ankle for 7 days during waking hours. Five days of data were plotted for average minutes per day spend at each stride rate from one stride per minute to the highest rate per participant. Time spent at each intensity level (strides/min) was represented in log-scale with a lowest curve fit for visualization of the youth with CP by GMFCS level and YDT. Y axis is the natural log and average strides taken with X axis the # of strides/minute.
Results: Youth with CP at level I on average were as active, have similar stride/min rates between <20 and >60 strides and are capable of peak stride rates (85 strides/min) similar to YDT. Their primarily limitation appears in stride/min rates between 20 and 60 strides [Fig H1]. Participants at Level II were less active on a daily basis demonstrating rates consistently lower than the YDT peaking at 75 strides/min as documented by a initially steeper curve that remains flat. Youth at level III demonstrate a low level of daily activity with the average stride rates outside the confidence band for YDT between 10 and 50 with a peak stride/min of 70.
Conclusions/Significance: Day to day walking activity of youth with CP demonstrates characteristic patterns of lower levels of walking activity, intensity levels across stride rates and peak stride rates than YDT as expected by GMFCS level. Youth with CP are more heterogeneous across stride rates than YDT. Ambulatory activity curves with the StepWatch have the potential to capture levels of daily ambulatory function temporally as well as in terms of intensity. This `snapshot’ analysis of average daily walking activity patterns may have application for clinical practice and/or outcome research.

 
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