Research has underscored the need to generate a clear and coherent theoretical underpinning relating to the social processes attached to involvement in fitness training and organized sports when engaging in young adult offender community reintegration supports. The research utilized a collective and instrumental case study approach to explore the learning and associational experiences of Irish young adult male offenders’ participation in fitness training and organized sports during community reintegration. Grounded theory was used to guide and analyze the research, which involved nine in-depth interviews with adult male participants engaging in two community reintegration projects. The emergent theory presents a winding trajectory of prior positive experiences with sports during childhood, rejection of positive leisure activities while engaging in substance use and crime, and the importance of fitness training and sports in providing a new pro-social identity and daily routine while reintegrating. Solitary and compulsive participation was common, with certain sports imparting new values, discipline, and coping mechanisms. Findings can be used to improve lifestyle and sports programs designed to support young adult offenders.