Participation in regular physical activity is recognized as a necessary contributor to health and well-being for children and adolescents with cerebral palsy (CP). Over recent years the number of papers on this topic has increased, attesting to the importance being afforded this issue. Despite this interest, research investigating the psychometric properties of measures of physical activity in individuals with CP has been relatively limited. This is of concern, as the underpinning of a good study design lies in the selection of measures which are known to be valid, reliable, and responsive to change in the population studied. Research in typically developing children supports the use of pedometers and accelerometers to accurately record physical activity.[1] However, differences in gait biomechanics and energy expenditure means that specific validation is required for children and adolescents with CP.

Systematic reviews on measurement of physical activity in individuals with CP have drawn limited conclusions other than to plead for additional high quality research. When the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN)[2] criteria have been applied, studies investigating the validity of measures of physical activity ranged from Fair to Poor in quality, with little evidence to support the reliability of these measures in children with CP.[3] Maher et al.[4] answer this call, providing a robust evaluation of the NL-1000 pedometer (New Lifestyles Inc., Lee's Summit, MO, USA). The authors have carefully considered their study design and reporting, enabling readers to interpret these results with confidence. Application of the COSMIN criteria to this paper rates the overall study quality as Excellent, with the exception of the description of missing data handling (which was Good). Rigorous statistical testing has been applied, sample size justified, and their findings carefully interpreted to highlight that the results apply to independently ambulant children, classified at Gross Motor Functional Classification System (GMFCS) levels I or II, and under controlled settings only. The accuracy of the NL-1000 in an individual classified at GMFCS level III, who walks with an external support and typically in a more crouched position, may be quite different and should be investigated separately.

Future research that considers the measurement of physical activity in individuals across all GMFCS levels is required, but when doing so it is important to consider if step counts provide a relevant measure of physical activity for all. For an individual using primarily wheeled mobility, a step counting device is of limited use, given that the majority of physical activity performed would be missed by a pedometer. Accelerometers have an advantage in that they can be either wrist or waist mounted, meaning they are appropriate for children across all GMFCS levels, and most importantly provide data on activity intensity, which has been validated against energy expenditure in ambulant children and adolescents with CP.[5] In addition, preliminary work in typically developing children suggests that pattern recognition can be applied to raw accelerometer data, which can be used to determine time spent in various activities, such as sitting, lying, walking, or running.[6] This could be the way forward for measurement of physical activity, as different intensity levels can be applied to each activity type meaning accuracy could be improved.

Maher et al. also highlight that their findings apply only to controlled settings. This is an important distinction, as during free play in a naturalistic environment an individual is likely to transition quickly between different movements or postures and at varying speeds. While methodologically more challenging, the accuracy of pedometers or accelerometers in a naturalistic setting is important to ascertain. Knowledge that performance of physical activity can be measured accurately in the ‘real world’ is vital, as ultimately it is the performance in this environment that will provide the benefits to health and well-being that we hope to achieve.


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  2. References
  • 1
    Trost SG. State of the art reviews: measurement of physical activity in children and adolescents. Am J Lifestyle Med 2007; 1: 299314.
  • 2
    Terwee CB, Mokkink LB, Knol DL, Ostelo RW, Bouter LM, de Vet HC. Rating the methodological quality in systematic reviews of studies on measurement properties: a scoring system for the COSMIN checklist. Qual Life Res 2012; 21: 6517.
  • 3
    Mitchell LE, Ziviani J, Oftedal S, Boyd RN. A systematic review of the clinimetric properties of measures of habitual physical activity in primary school aged children with cerebral palsy. Res Dev Disabil 2013; 34: 24192432.
  • 4
    Maher C, Kenyon A, McEvoy M, Sprod J. The reliability and validity of a research-grade pedometer for children and adolescents with cerebral palsy. Dev Med Child Neurol 2013; 55: 827832.
  • 5
    Clanchy KM, Tweedy SM, Boyd RN, Trost SG. Validity of accelerometry in ambulatory children and adolescents with cerebral palsy. Eur J Appl Physiol 2011; 111: 29519.
  • 6
    Trost SG, Wong WK, Pfeiffer KA, Zheng Y. Artificial neural networks to predict activity type and energy expenditure in youth. Med Sci Sports Exerc 2012; 44: 18019.