Reliability and Validity of Objective Measures of Physical Activity in Youth With Cerebral Palsy Who Are Ambulatory

Margaret E. O'Neil; Maria Fragala-Pinkham; Nancy Lennon; Ameeka George; Jeffrey Forman; Stewart G. Trost

doi:10.2522/ptj.20140201

Abstract

Background Physical therapy for youth with cerebral palsy (CP) who are ambulatory includes interventions to increase functional mobility and participation in physical activity (PA). Thus, reliable and valid measures are needed to document PA in youth with CP.

Objective The purpose of this study was to evaluate the inter-instrument reliability and concurrent validity of 3 accelerometer-based motion sensors with indirect calorimetry as the criterion for measuring PA intensity in youth with CP.

Methods Fifty-seven youth with CP (mean age=12.5 years, SD=3.3; 51% female; 49.1% with spastic hemiplegia) participated. Inclusion criteria were: aged 6 to 20 years, ambulatory, Gross Motor Function Classification System (GMFCS) levels I through III, able to follow directions, and able to complete the full PA protocol. Protocol activities included standardized activity trials with increasing PA intensity (resting, writing, household chores, active video games, and walking at 3 self-selected speeds), as measured by weight-relative oxygen uptake (in mL/kg/min). During each trial, participants wore bilateral accelerometers on the upper arms, waist/hip, and ankle and a portable indirect calorimeter. Intraclass coefficient correlations (ICCs) were calculated to evaluate inter-instrument reliability (left-to-right accelerometer placement). Spearman correlations were used to examine concurrent validity between accelerometer output (activity and step counts) and indirect calorimetry. Friedman analyses of variance with post hoc pair-wise analyses were conducted to examine the validity of accelerometers to discriminate PA intensity across activity trials.

Results All accelerometers exhibited excellent inter-instrument reliability (ICC=.94–.99) and good concurrent validity (rho=.70–.85). All accelerometers discriminated PA intensity across most activity trials.

Limitations This PA protocol consisted of controlled activity trials.

Conclusions Accelerometers provide valid and reliable measures of PA intensity among youth with CP.

Footnotes

Dr O'Neil, Dr Fragala-Pinkham, and Dr Trost provided concept/idea/research design. Dr O'Neil, Dr Fragala-Pinkham, Ms Lennon, and Dr Trost provided writing and project management. Dr O'Neil, Dr Fragala-Pinkham, Ms Lennon, and Ms George provided data collection. Dr O'Neil, Dr Fragala-Pinkham, Ms Lennon, Ms George, and Dr Trost provided data analysis. Dr O'Neil and Dr Fragala-Pinkham provided fund procurement. Dr Fragala-Pinkham, Ms Lennon, and Dr Forman provided participants, facilities/equipment, institutional liaisons, and consultation (including review of manuscript before submission).
Institutional review board approval was obtained from Franciscan Hospital for Children (Brighton, Massachusetts), Drexel University (Philadelphia, Pennsylvania), and Nemours/Alfred I. duPont Hospital for Children (Wilmington, Delaware).
Funding for this project was provided by an NIH R24 Resource-Related Research Projects Grant awarded to Boston University, Boston Rehabilitation Outcomes Center (Boston ROC), titled “Improving Outcome Measurement for Medical Rehabilitation Clinical Trials.”