Jayden Miller, Matthew Kwan

Physical activity (PA) declines sharply during the transition into early adulthood, with more than 80% of individuals aged 18-24 failing to meet international PA guidelines. University entry is a vulnerable period, as academic demands, disrupted routines, residential transitions, and limited access to supportive spaces contribute to reduced movement. While individual-level determinants of PA are well-documented, growing evidence highlights the role of built environments (BEs), including walkability, greenspace, and access to recreation, in shaping activity behaviours. However, most BE-PA research relies on static, residence-based indicators and self-reported PA, which fail to capture real-time environmental exposures. University students move through diverse physical contexts, yet little is known about how moment-to-moment exposure relates to acute PA.This study addresses this gap using a 14-day intensive longitudinal design with 50 undergraduate students who will wear Apple Watches to collect minute-level PA and passive GPS data. Data will be harmonized using Pathverse, with GPS trajectories linked to GIS-derived BE features. Static BE exposure will be assessed using the Canadian Active Living Environments index at residential locations, while dynamic exposure will be quantified by linking GPS points to environmental contexts encountered during daily routines. Daily mobility metrics, including distance travelled and locations visited, will be derived from GPS data. Multilevel mixed-effects models will examine associations between BE exposure, mobility patterns, and momentary and day-level PA outcomes. By integrating wearable accelerometry, passive GPS sensing, and geospatial analytics, this research provides ecologically valid, high-resolution evidence on how BE’s support or inhibit physical activity among university students.