This doctoral thesis examines the stages of change model (SOC) in the field of sports for patients with chronic polyarthritis (70 %) or spondyloarthritis (30 %). Cross-sectional and longitudinal data of 294 rehab patients were analysed. The analysis of discontinuity patterns of the cognitive and behavioural components (self-efficacy, perceived benefits and barriers, sports activities) across the stages (precontemplation, contemplation, preparation, action, maintenance) was focused to verify qualitative different stages of change. As hypothesized, self-efficacy and perceived benefits increased within higher stages of change, while perceived barriers decreased. Sports activities were reported more frequently by patients at higher stages. Discontinuity patterns were proven to some extent. The SOC model holds great potential for interventions to support exercise and sports in the target group, but it needs further validation against more representative samples.