Determinants, measurement and promotion of physical activity in 10-14 year-old Bedfordshire children: a multidisciplinary approach

A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Doctor of PhilosophyRegular moderate-vigorous physical activity (MVPA) is associated with significant physiological and psychological health benefits (Department of Health, DoH, 2004). However, many children are not undertaking recommended levels of physical activity (PA) (DoH, 2009). This research examined relationships between physiological health parameters, psychological determinants and PA levels in 10-14 year old schoolchildren (N = 249) and assessed the influence of three school-based PA interventions on these constructs in the context of the Health And Physical activity Promotion in Youth (HAPPY) study. Study 1 revealed that sedentary behaviours, moderate PA (MPA), vigorous PA (VPA) and MVPA levels were higher on weekdays than weekend days (p < .001). However, schoolchildren’s PA is often difficult to measure accurately. The self-report measure utilised in study 2 underestimated total MVPA versus accelerometry for both sexes on weekdays and girls on weekend days (p < .01). However, study 3 highlighted a lack of agreement between two RT3® triaxial accelerometer cut-offs for all activity categories. The importance of VPA for promoting health was highlighted in the updated PA guidelines (DoH, 2011). Study 4 reported that cardiorespiratory fitness (CRF) was positively associated with VPA but not MPA (β = .27, p < .01) and inversely correlated with measures of body composition (% body fat; body mass index; waist circumference) (r = -.74, r = -.60, r = -.39, p < .001). Knowing the health benefits of regular MVPA and VPA, it is important to understand the determinants of PA intentions and behaviours to more effectively promote PA in less active children (studies 5 and 6). An exploratory analysis of the constructs in the Revised Theory of Planned Behaviour and the Modified Social Learning Theory for children predicted PA intentions (R2 = .38, F(5, 171) = 20.19, p < .001; R2 = .13, F(6, 147) = 3.4, p < .01, respectively) but the constructs in either model were unable to predict PA. Recognising the need to promote PA levels, study 7 investigated the effectiveness of three school-based interventions (vs. control) on outcome variables included in studies 1, and 4-6. The Health Education and Psychology Health Promotion conditions produced significant positive change scores between data collection 2 and 3 for CRF (vs. control) whereas the Youth-Led condition produced significant change scores between baseline and data collection 2 for generalised self-efficacy (vs. control). No significant change scores were reported for PA, the RTPB constructs or intentions. In conclusion, this research has emphasised the importance of employing a multidisciplinary approach to aid understanding of schoolchildren’s PA levels. Specific highlights include low weekend day PA as a possible future PA promotion target, although it is vital that accelerometry cut-points are standardised, and the relevance of VPA and body composition in predicting CRF. The psychological models identified some important determinants of PA intentions, but a prominent intention-behaviour gap and a need for more intensive interventions to promote PA levels was apparent