Gabrielle D. Bedard, Jiangbo Yu, Audrey C. Wong, Zhiyang Shi, Jordan D. Herbison, Gordon A. Bloom, Jennifer R. Tomasone, Shane N. Sweet

University students with physical disabilities and chronic conditions often face barriers to physical activity behaviour change (e.g., fatigue, competing demands, and limited psychological bandwidth), which can shape how behaviour change techniques (BCTs) are enacted in daily life. Self-enactable BCTs (e.g., goal setting, self-talk) are designed to support behaviour change. However, little is known about how individuals cognitively (e.g., mindset, decision-making, perfectionistic thinking) and emotionally (e.g., shame, guilt, confidence) experience BCT enactment outside structured interventions. This qualitative longitudinal study will explore how university students with physical disabilities and chronic conditions experience the cognitive and emotional processes involved in enacting BCTs. Ten university students will complete seven consecutive days of daily diary reflections, prompted by an generative AI-based agent, at the beginning, midpoint, and end of the academic term, with reflections focusing on physical activity participation, BCT use, and related cognitive and emotional experiences. Semi-structured interviews (~60 minutes) conducted midpoint, and end of the semester will support the co-construction of individual timelines based on diary entries, highlighting key moments in BCT enactment over time. Guided by an interpretivist stance, data will be analysed using reflexive thematic analysis with a hermeneutic phenomenological focus on lived emotional and cognitive experiences. Diary-informed timelines will be refined through interview dialogue, followed by cross-participant examination of cognitive and emotional patterns shaping BCT enactment and physical activity behaviour change. Findings may elucidate underlying psychological patterns shaping BCT enactment and behaviour change, informing for stronger physical activity behaviour change interventions for university students with physical disabilities and chronic conditions.