Title: Bristol Girls Dance Project: A cluster randomised controlled trial of an after-school dance programme to increase physical activity among 11-12 year old girls
Funder: Department of Health (England)

Abstract: Design: School-based cluster randomised controlled trial. Setting: 18 State secondary schools with Year 7 (aged 11-12) girls in the greater Bristol area. Target population: Year 7 girls in the target schools who provide informed parental consent. Intervention being evaluated: Schools randomised to the intervention (N=9; 270 children) will be provided with a 20-week (i.e. 2 school terms) dance intervention. The dance programme will be delivered twice a week at the school site. Each session will last 75 minutes and will be delivered by external dance teachers using a standardised programme. The dance programme focuses on building the girls’ perceived autonomy to be active and perceived dance competence in a social mutually supportive environment. All outcomes will be assessed at three time points: baseline (time 0) during weeks 19-20 of the intervention period (1st follow-up) and a year after baseline data have been collected (2nd follow-up = time 0 + 52 weeks). The primary comparison is the 2nd follow-up which is designed to ascertain whether any beneficial effect of the intervention remains once the intervention has been removed. The 1st follow-up is designed to yield information on activity levels while the programme is still running. All baseline (time 0) assessments will be conducted prior to school randomisation. The following outcomes will be assessed at each stage:1)Primary: Accelerometer derived mean minutes of moderate to vigorous intensity physical activity (MVPA) on a weekday will be our primary outcome measure. Secondary outcomes2)The following accelerometer derived variables will be considered secondary outcomes: a) Mean weekend minutes of MVPA; b) Mean weekday accelerometer counts per minute (which provides an indication of the volume of activity in which the girls engage); c) Mean weekend accelerometer counts per minute. In addition we will also compute mean minutes of sedentary time per weekday (<100 counts per minute). We will also assess self-reported autonomy competence relatedness perceived parental support and self esteem which we are hypothesising may function as mediators of behaviour change. 3)Intervention related resource use in the form of time travel and expenses will be collected through researcher and dance teacher timesheets from a public sector perspective (Local Authorities NHS). Researchers will record expenses connected with intervention delivery. 4)Process assessments will be undertaken to assess the dose of intervention delivered intervention fidelity and the potential dissemination of the intervention. Attendance at each session session duration and session lesson plan compliance will be reported by the dance instructors. The dose of the intervention (i.e. number of planned sessions delivered) will be recorded in each school. Intervention fidelity will be assessed by two methods: a) dance teachers will complete a log-book indicating whether they delivered planned core components of each session either fully partially or not at all; and b) four randomly selected sessions delivered by each dance teacher will be observed during the 20 week intervention. At the end of these sessions we will also ask all girls to complete a brief perceived exertion and enjoyment questionnaire.5)Qualitative work to assess potential sustainability and dissemination of the intervention. Exit interviews will be conducted with each of the dance instructors and a member of the school leadership (Headteacher / Year head etc) at each intervention school. We will also conduct two focus groups with six participants at six of the intervention schools. Focus group participants will be purposively sampled to include girls with high and low attendance levels. Sample size: The target difference for this trial is 10 minutes of MVPA per weekday (i.e. 50 minutes per week) between the intervention and control groups. This magnitude of effect is achievable with this intervention based on our pilot study data. The uninflated sample size required for analysis to detect a difference of 10 minutes/day MVPA assuming a standard deviation of 18 minutes with 90% power and 5% two-sided alpha is n=68 per arm. We estimated the 95% CI for the school-associated ICC in the pilot study to be <0.001 to 0.087. If we assume that 20% of participants will not provide primary outcome data the mean cluster size for analysis will be 24 resulting in a design effect of 3.0 using the upper 95% confidence limit for ICC. Thus we will recruit a total of 18 schools and 540 children.Randomisation: This is a clustered randomised trial with allocation of schools and analysis at the level of the individual. Allocation will be performed by a statistician with no other involvement in the study and balanced according to baseline levels of MVPA. Planned analyses: The analysis and presentation of the trial will be in accordance with CONSORT guidelines with the primary comparative analyses being conducted on an intention-to-treat basis and due emphasis placed on confidence intervals for the between-arm comparisons. A full analysis plan will be developed prior to completion of data collection and discussed and agreed with the TSC. We will use descriptive statistics to assess balance between the trial arms at baseline for both school and individual participant characteristics. The primary outcome will be analysed by intention to treat without imputation. In order to take appropriate account of the hierarchical nature of the data we will use multivariable mixed effects linear regression to estimate difference in the primary outcome for intervention group versus control adjusting for baseline MVPA and randomisation variables. In a secondary analysis we will further adjust for any variables that were imbalanced between the trial arms at baseline. Similar analyses will be repeated for secondary outcomes. We will conduct sensitivity analyses to assess the potential effect of missing data using multiple imputation.


Research activity codes: 3.1 PRIMARY PREVENTION INTERVENTIONS TO MODIFY BEHAVIOURS OR PROMOTE WELL-BEING
Health categories: STROKE;CANCER AND NEOPLASMS;METABOLIC AND ENDOCRINE;CARDIOVASCULAR;ORAL AND GASTROINTESTINAL