Discussion
SESSION
This longitudinal qualitative study identified three central themes over the 24-month period, all related to SDT: Autonomy, Competence and Relatedness. Session leaders supported participants in adapting REACT exercise to the home environment and encouraged the adoption of self-regulatory strategies such as self-monitoring, action-planning and problem-solving. Participants reported that having control over their participation in REACT, supported by session leaders, was key to adoption (six-months) and to long-term (12-months) REACT participation. The importance of control here, supports literature highlighting that autonomous rather than controlled motivation is key to behavioural adoption and maintenance [Improvements in competence were reported at each timepoint throughout the REACT programme. However, the source of this competence and the subsequent motivation for further PA participation varies across the three time points. At six-months, competence was derived externally from Session Leaders and REACT peers. At 12-and-24-months, competence was derived from personal capability and improvements in physical, social and mental health (i.e. participants attributed improved mobility to increased PA and recognised the importance of active living in maintaining improvements). There was a clear distinction between types of motivation (controlled and autonomous) and internalisation of motivation during REACT. The distinction between types of motivation supports existing literature that extrinsic motivation may be more important in the adoption stage of PA behaviour change with internalisation of motivation being important for sustained behaviour change [Participants identified factors commonly cited in the literature as positively affecting competence-related motivation: (a) support to try new classes, (b) breaking down and adapting exercises to suit individual capabilities, (c) use of self-regulatory techniques (self-monitoring and problem-solving) to break down barriers and sustain motivation over time. These self-regulation strategies are reported by several systematic reviews and meta-analyses to be determinants of successful PA interventions [Participants reported a sense of relatedness/social connectedness to both REACT session leaders and their REACT peers. Relatedness was facilitated by exercise that was enjoyable and sociable [Relatedness was equally important at 12-months as it was at six months. Increased relatedness motivated participants to adhere to REACT and maintain relationships among group members, consistent with existing literature highlighting participant relatedness as an important determinant of adherence [Session leader support for social interaction and the commitment participants felt to the session leader and REACT peers are commonly cited in the literature as important components of successful active aging programmes [