The promotion of physical activity to young people is currently a public health priority due to growing concerns that this group is not sufficiently physically active. Adolescence in particular is characterised with a decline in physical activity levels (Verstraete, et al 2006, Journal of Public Health, 16: 415-419). There exists an increased concern that Physical Education lessons within the National School Curriculum do not assist with this downward trend in activity levels, thus the notion of using school break time to promote physical activity is being explored (Ridgers, et al 2006, Sports Medicine, 36: 359-371). Whilst research has been completed into the use of break time physical activity interventions within primary schools, there is a distinct shortage of work examining the effectiveness of interventions aimed at the adolescent population. The aim of this study was to hence establish if a physical activity intervention delivered in school break time could increase the physical activity levels of adolescents from one secondary school in Lincoln. Emphasis was placed upon evaluating the intervention in order to establish its effectiveness and not merely reporting statistical findings. The research was situated within the critical realist paradigm adopting a subjective epistemology. Following institutional ethics approval, one secondary school was chosen as the case study location. Observations recording adolescents’ physical activity levels were completed during lunch break twice per week for a period of five weeks using the System for Observing Play and Leisure Activity in Youth (SOPLAY). The first two weeks featured no physical activity intervention, whilst the final three weeks involved the provision of games equipment. Structured interviews were completed with adolescents to gain a deeper understanding of the influence and effect of the intervention on physical activity levels. Both data sets were then incorporated to evaluate the effect of the intervention under the RE-AIM Evaluation Framework (Glasgow, et al 1999, American Journal of Public Health, 89: 1322-1327). Findings illustrated that the intervention had no significant impact on break time physical activity levels and that physical activity was limited due to institutional constraints placed by the school. Restraints related to the time available at break time which reduced activity opportunities, especially when considering the time adolescents required to leave and return to lessons. The study thus suggests that it is the school environment as opposed to the activity available which influences adolescents’ physical activity levels at break time
