Childhood obesity is a rising health concern in the UK associated with reduced physical function and physical well-being. Exercise interventions targeting paediatric obese populations report low attendance and adherence and often neglect the experience and needs of children. The purpose of this thesis is to review previous intervention research in consideration of reported associations between childhood obesity, physical function, and physical well-being, combined with exercise theory for strength and postural stability development, to design an intervention for delivery in primary schools. The aims of this thesis were to first assess the reliability and change statistics of key physical function measures, including isokinetic dynamometry, clinical physical function, and 3D gait assessment, in children with overweight and obesity (OWB). Secondly, to design, pilot, and refine a feasible, school-based exercise intervention aimed at improving postural stability and muscular strength in children with OWB while also addressing the psychological needs of children with OWB. Finally, to evaluate the effectiveness of this intervention (Co-produced with children with OWB targeting Postural stability and muscular Strength: COPS intervention) and to determine the impact on physical well-being and physical function. The reliability study assessed laboratory and clinical assessment of children's (n=22) physical function using a 1-week test-retest design, focusing on minimally detectable change (MDC) statistics. A pilot of an eight-week intervention with 14 children with OWB (intervention group n = 7, control group n = 7) was conducted to examine intervention feasibility and effectiveness, with emphasis on children's reported enjoyment and need satisfaction. Following the pilot phase, a co-production approach, collaborating directly with children (n = 12), addressed identified challenges from the pilot. The eight-week COPS intervention was then delivered in five schools (intervention group n = 22, control group n = 17). Children with OWB exhibited greater reliability and lower MDC statistics compared to typical weight (TW) peers. Additionally, children with OWB demonstrate greater variability in gait, likely due to the challenges of controlling and moving their larger mass. The pilot study revealed that children's motivation may play a critical role in intervention effectiveness as this results in low attendance and adherence, limiting any beneficial result to physical function and physical well-being measures. Interventions for children should meet the needs of children for motivation and enjoyment, and this may be even more important for children with OWB, who generally engage in less activity. A co-production approach allowed for intervention refinement by altering the delivery format, exercise variation and means to track engagement, aligning with children's preferences and needs. The concluding COPS intervention demonstrated sustained engagement and higher activity intensity levels than typical physical education classes. Pre-intervention, post-intervention, and follow-up laboratory and clinical physical function assessments showed the COPS intervention to have improved performance in lower limb muscle strength, as well as performance in clinical physical function tests. The research highlights the promising effects of a co-production approach to intervention development in school-based exercise interventions and the potential benefits of strength and postural stability focused exercise to children with OWB's physical function. This work provides support for child-centred and evidenced-based active play that may help inform teaching styles (i.e. autonomous supportive environments), PE curriculum design (i.e. prioritising play and activity with the broader aim of physical function over sports skills) and future research (i.e. further intervention adaptation, examination of the role of motor co-ordination and relationships of physical function and physical well-being in children with OWB).
