Research design and data sources
The study was a part of a 5-year prospective randomized controlled trial intervention study implemented within 30 pre-existing ASPs, comparing a social-motivational development physical activity program to a health curriculum active control. A total of 10 ASPs in Year 1 and 2 were randomly sampled with stratification criteria that ensured the ASP sampling pool represented underserved communities (enrollment includes at least 50% of youth from low-income households, defined by free/reduced lunch status, and of minority status). From the resultant stratified sampling pool, 5 sites were randomly assigned to the experimental condition to offer adolescents the PA social-motivational climate intervention curriculum. Given the purpose of the study, only data from the intervention condition were analyzed and reported in which the social-motivational climate was implemented as part of the intervention. A repeated measures design was used for the current study to test whether the intervention has the potential to cause change. The Connect through PLAY intervention was administered three days a week for 16 weeks. The baseline data were collected prior to the intervention, the midpoint data were collected at the middle of the intervention (8-week), and the endpoint data were collected following the completion of the intervention. The data collection protocols and data protection procedures, along with parent consent forms and student assent forms, were approved by the University (masked) Internal Review Board prior to data collection.Given the particularly heightened need and orientation toward social connection, social feedback, and social self-preservation that is characteristic of early adolescence, the intervention was novel in that it focused on facilitating key social mechanisms to support youth self-determined motivation including: (a) building friendships (supporting PA competence, autonomy, and relatedness through encouraging close, mutual relationships with others); (b) promoting group belonging (supporting feelings of being liked and accepted by peers and of being a valued member/contributor to the program, through the establishment of positive peer PA norms, inclusiveness, and tangible PA social support); and (c) fostering staff-youth connections (feeling connected to, supported, and encouraged by staff; see Authors Masked).