Conclusions
Our findings suggest that need-supportive environments that foster feelings of autonomy, competence and relatedness promote adherence to a structured, group-based exercise and behavioural maintenance programme. A transition from extrinsic motivation to intrinsic motivation and internalisation of feelings of competence (which were further strengthened by experiences of physical, mental and social benefits) were important for continuing engagement with the REACT programme and maintenance of an active lifestyle post-intervention. PA interventions for older adults should incorporate activities that are enjoyable and need-supportive; (a) making exercise social and enjoyable, (b) understanding participants’ capabilities and tailoring the programme accordingly, (c) capitalising on group support to motivate participants to try other activities and prepare sustainable active living plans. Further longitudinal qualitative research will allow us to understand how these (and other) processes impact engagement with a wider range of community-based activities, particularly focussing on older people with compromised mobility and older people who experience loneliness and/or social isolation.