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Title: Body mass index and accelerometer measurement issues for use in the evaluation of pedometer-based physical interventions in children
Author: Routen, Ashley
Awarding Body: University of Worcester
Current Institution: University of Worcester
Date of Award: 2013
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Participation in physical activity (PA) of at least moderate intensity may yield important health benefits for children. A popular behavioural tool used to promote increased PA is the pedometer. There is however limited evidence regarding pedometer-based strategies in children. This thesis reports on a series of anthropometric and accelerometer-measurement issue studies which inform the methods used to address the primary aim of this thesis- to determine the effectiveness of goal-setting, selfmonitoring and step-feedback pedometer-based interventions for increasing PA in 10- 11-year-old children. In addition, each study in their own right provides an original contribution to knowledge within their specific area of scholarship. The first objective of this thesis was therefore to determine diurnal variation of height and weight and the combined effect upon body mass index (BMI) weight status in children via a field based study. Next, the reliability of the Actiwatch 4 (AW4) accelerometer was tested in a mechanical laboratory experiment. Following this laboratory trial a second field based study examined the impact of placement site upon AW4 output, and the validity of a regression equation to predict hip-derived AW4 data from wrist-derived data. Finally, a brief intervention mapping approach was used to develop goal-setting, selfmonitoring and step-feedback pedometer-based interventions, the effectiveness of which was evaluated in a small scale controlled trial involving two primary schools. The main findings of this thesis were a) that diurnal variation in height (and in girls alone, weight) impact upon increased BMI and BMI percentile in afternoon versus morning measurements b) AW4 activity counts exhibit acceptable reliability statistics (comparable to other accelerometer models), which improve when raw activity counts are reduced into derived activity intensity variables c) wrist and hip derived AW4 data are not comparable, and the derived regression equation may not be suitable for group level prediction due to inaccurate individual level prediction and the large standard error of the estimate observed d) pilot testing pedometer wear and intervention materials may highlight practical pedometer issues (i.e. pedometer attachment, wearing compliance and acceptability of instruction sheets) that inform intervention implementation and e) pedometer-based goal-setting, self-monitoring and step-feedback interventions did not increase PA in 10-11-year-old children. However, individual-standardised goal setting may be more promising as this appeared to mitigate any decline in moderate-to-vigorous physical activity (MVPA) in moreactive children, and increased MVPA in less-active. To summarise, the findings of this thesis highlight important issues for physical activity scientists to consider when using BMI-determined weight status as a grouping variable and accelerometers as an outcome measure, when evaluating physical activity interventions in children. With regard to the primary aim of this thesis, future researchers should further examine the effectiveness of the individual-standardised against the group-standardised goal type in a longer-duration intervention and using a larger sample of children, which may permit sub-group analyses to be conducted. Of primary importance is future clarification on the effectiveness of goal setting, self-monitoring and step-feedback pedometer-based interventions per se for changing PA in children.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: RJ101 Child Health. Child health services