Dissertation - Doctoral The Development of Outcome Measures and Identification of Effective Behavioural Modification Strategies to Study the Efficacy of Habitual Physical Activity on Health Outcome in  Children with Chronic Disease


Samantha Stephens


Background Physical activity (PA) may play an integral role in improving the quality of life of children with chronic conditions by ameliorating disease symptoms, preventing the onset of disability and reducing secondary disease risk. A lack of valid outcome measures, tools and behavioral strategies to implement PA interventions negatively impacts the quality of studies.

Objective The objective of this thesis was to determine the validity of PA outcome measures, tools to identify readiness to take part in physical activity, as well as to determine the efficacy of behavioral theories and techniques for increasing PA in children with chronic conditions.

Methods The validity of accelerometry, a PA measurement tool, was studied by comparing accelerometer output to a gold standard measure of energy expenditure. Strategies for dealing with missing data from accelerometers were synthesized in a review of the literature. The face, content and construct validity of the stage of exercise scale (SOES), used to identify readiness to exercise, was examined by studying the relationships among SOES and it’s theoretical constructs. Finally, the efficacy of behavioral techniques and theories applied to interventions to increase PA was identified by systematic review.

Results Pre-existing accelerometer equations and cut points are not valid for children with chronic conditions. In response, disease specific equations and cut points were developed. Multiple imputation demonstrated the least bias in replacing missing accelerometer data. The SOES demonstrated acceptable face, content and construct validity. Physical activity interventions demonstrated a small effect on increasing PA levels. Overall, theory informed interventions did not demonstrate a significant effect. Social Cognitive Theory demonstrated limited efficacy with strongest evidence for behavioral techniques associated with goals and planning.

Conclusions This thesis has contributed tools, measures and strategies that are valid, accurate and efficacious that will facilitate the delivery of PA interventions to children with chronic conditions.


Brian Feldman