The benefits of physical activity are well-established. However, adherence to and sustained participation remain limited. These difficulties are partly explained by a lack of consideration for individual differences and the psychosocial factors influencing motivation and participation. Models from the psychology of motivation, such as the transtheoretical model of change, emphasize the importance of support tailored to each individual's level of commitment and personal needs. From this perspective, social design, based on co-creation and the active participation of users, could be a promising approach for individualizing interventions with defined, sustainable, and replicable methodologies. By involving seniors in the design and adjustment of programs, this approach promotes autonomy, a sense of competence, and long-term continuity of practice. Thus, the objective of this study is to determine the effects of co-created physical activity programs with participants on program adherence and long-term physical activity adoption. The hypothesis is that co-created physical activity would lead to better adherence and long-term commitment.