title: Using self-determination theory to promote adolescent girls' physical activity: Exploring the theoretical fidelity of the Bristol Girls Dance Project.
abstract: OBJECTIVE
  To report the theory-based process evaluation of the Bristol Girls' Dance Project, a cluster-randomised controlled trial to increase adolescent girls' physical activity.
  
  
  METHODS
  A mixed-method process evaluation of the intervention's self-determination theory components comprising lesson observations, post-intervention interviews and focus groups.
  
  
  METHODS
  Four intervention dance lessons per dance instructor were observed, audio recorded and rated to estimate the use of need-supportive teaching strategies. Intervention participants (n = 281) reported their dance instructors' provision of autonomy-support. Semi-structured interviews with the dance instructors (n = 10) explored fidelity to the theory and focus groups were conducted with participants (n = 59) in each school to explore their receipt of the intervention and views on the dance instructors' motivating style.
  
  
  RESULTS
  Although instructors accepted the theory-based approach, intervention fidelity was variable. Relatedness support was the most commonly observed need-supportive teaching behaviour, provision of structure was moderate and autonomy-support was comparatively low. The qualitative findings identified how instructors supported competence and developed trusting relationships with participants. Fidelity was challenged where autonomy provision was limited to option choices rather than input into the pace or direction of lessons and where controlling teaching styles were adopted, often to manage disruptive behaviour.
  
  
  CONCLUSIONS
  The successes and challenges to achieving theoretical fidelity in the Bristol Girls' Dance Project may help explain the intervention effects and can more broadly inform the design of theory-based complex interventions aimed at increasing young people's physical activity in after-school settings.
authors.affiliation: Centre for Exercise, Nutrition & Health Sciences, School for Policy Studies, University of Bristol, 8 Priory Road, Bristol, BS8 1TZ, UK.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Sebire
authors.affiliation: Centre for Exercise, Nutrition & Health Sciences, School for Policy Studies, University of Bristol, 8 Priory Road, Bristol, BS8 1TZ, UK.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Kesten
authors.affiliation: Centre for Exercise, Nutrition & Health Sciences, School for Policy Studies, University of Bristol, 8 Priory Road, Bristol, BS8 1TZ, UK.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Edwards
authors.affiliation: Centre for Exercise, Nutrition & Health Sciences, School for Policy Studies, University of Bristol, 8 Priory Road, Bristol, BS8 1TZ, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: May
authors.affiliation: Centre for Exercise, Nutrition & Health Sciences, School for Policy Studies, University of Bristol, 8 Priory Road, Bristol, BS8 1TZ, UK.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Banfield
authors.affiliation: Bristol Randomised Trials Collaboration, School of Social & Community Medicine, University of Bristol, Bristol, BS8 2PS, UK.
authors.forename: Keeley
authors.initials: K
authors.lastname: Tomkinson
authors.affiliation: Bristol Randomised Trials Collaboration, School of Social & Community Medicine, University of Bristol, Bristol, BS8 2PS, UK.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Blair
authors.affiliation: Health and Social Sciences, University of the West of England, Bristol, UK.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Bird
authors.affiliation: Health and Social Sciences, University of the West of England, Bristol, UK.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Powell
authors.affiliation: Centre for Exercise, Nutrition & Health Sciences, School for Policy Studies, University of Bristol, 8 Priory Road, Bristol, BS8 1TZ, UK.
authors.forename: Russell
authors.initials: R
authors.lastname: Jago
keywords: Adolescents; Intervention; Physical activity; Process evaluation; Self-determination theory