Webber 2008.

Study characteristics
Methods	Study design: cluster‐RCT
Participants	School inclusion criteria: public middle schools at which a majority of students lived in the surrounding community, enrolment of at least 90 grade 8 girls, yearly withdrawal rates < 28%, at least 1 semester of PE required for each grade, willingness to sign a memorandum of understanding and to accept random assignment of the school School exclusion criteria: none Student inclusion criteria: Grades 6, 7, and 8 female students Student exclusion criteria: limited English‐speaking skills, inability to participate in PE classes due to a medical condition or disability, contraindication for participating in a submaximal exercise test (2005 measurements only) Setting: community, school Age group: adolescents Gender distribution: females Country/Countries where trial was performed: USA
Interventions	Intervention: Trial of Activity for Adolescent Girls health education included 6 lessons in each of Grades 7 and 8 designed to enhance behavioural skills known to influence PA participation. Activity challenges associated with lessons reinforced the contents, encouraged self‐monitoring, and set goals for behaviour change. To meet varying formats in which health education was taught at the school, Trial of Activity for Adolescent Girls health education was offered in 2 forms: 1 for a traditional classroom setting and 1 for a PE class. Trial of Activity for Adolescent Girls PE class promoted MVPA for at least 50% of class time and encouraged teachers to promote PA outside of class. Activities targeted to create: environmental and organisational changes supportive of PA; and cues, messages, and incentives to be more physically active Specifically, the intervention was designed to establish more opportunities, improve social support and norms, and increase self‐efficacy, outcome expectations, and behavioural skills to foster greater MVPA. 35 to 40 girls were the focus of the intervention; however, health and PE classes were part of the usual school curriculum, and most included boys as well. An innovative feature of the intervention was linking school and community agencies to develop and promote PA programmes for girls. These programmes were delivered both on and off school property, in most cases before or after school Comparator: — Duration of intervention: 2 years Duration of follow‐up: 2 years Number of schools: 36 Theoretical framework: social cognitive theory, diffusion of innovation, operant learning theory
Outcomes	PA duration Sedentary time BMI
Study registration	NCT00006409
Publication details	Language of publication: English Funding: non‐commercial funding (National Heart, Lung, and Blood Institute) Publication status: peer‐reviewed journal
Stated aim for study	"The primary aim of Trial of Activity for Adolescent Girls was to test an intervention to reduce by half the observed decline in MVPA experienced by adolescent girls"
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Comment: computer generated [author communication]
Allocation concealment (selection bias)	Low risk	Comment: all participants were allocated at a single point in time following recruitment, so at time of recruitment, allocation was not known
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: no information given
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote from publication: “Trial of Activity for Adolescent Girls staff was blinded to the study outcomes until the 2006 data collection was complete. Also, separate intervention and measurement staff were employed” (Webber 2008, p174)
Incomplete outcome data (attrition bias) Anthropometrics, Fitness	High risk	Comment: incomplete outcome data; not addressed adequately Quote from publication: “in a study such as Trial of Activity for Adolescent Girls, efforts to obtain a complete set of measurements on the girls assigned to each treatment condition would require considerable resources, as it is expensive to track and measure students who have left a school. Furthermore, despite extraordinary efforts, ascertainment of measurements in every girl in the cohort is unlikely” (Stevens 2005, p226)
Incomplete outcome data (attrition bias) Physical activity and sedentary time	High risk	Comment: incomplete outcome data; not addressed adequately Quote from publication: “in a study such as Trial of Activity for Adolescent Girls, efforts to obtain a complete set of measurements on the girls assigned to each treatment condition would require considerable resources, as it is expensive to track and measure students who have left a school. Furthermore, despite extraordinary efforts, ascertainment of measurements in every girl in the cohort is unlikely” (Stevens 2005, p226)
Selective reporting (reporting bias)	Low risk	Comment: all outcomes identified a priori were reported on
Cluster RCT ‐ Recruitment bias	Low risk	Quote from publication: "schools at each of the six field centres were randomised in equal numbers to either intervention or control condition after baseline measurements were collected"
Cluster RCT ‐ Baseline imbalance	Low risk	Comment: baseline differences were compared using mixed models, with students nested within schools nested within intervention [author communication]
Cluster RCT ‐ Loss of clusters	Low risk	Comment: no clusters lost to follow‐up
Cluster RCT ‐ Incorrect analysis	Low risk	Comment: clustering accounted for in the analysis