13 MAY 2026 (WED) 16:05 - 16:35

Where movement happens: A multi-sensor study of urban environment, indoor and outdoor physical activity, and health in Hong Kong

Miss LI Tianyu   

( Supervisor: Prof Yanjia Cao )

Abstract:

Urbanization has profoundly reshaped daily living environments, exposing residents to both adverse environments, such as traffic noise and air pollution, and restorative environments, such as green space, each with distinct effects on physiological stress and mental wellbeing. In addition to these direct effects, physical activity has been identified as a critical mediator between built environment characteristics and mental wellbeing, with existing evidence indicating that neighborhood connectivity and pedestrian infrastructure improve mental health outcomes through increased physical activity engagement. These relationships are, however, critically influenced by urban morphology at the same time. In high-density cities, high-rise buildings, elevated footbridges, and underground passages create complex three-dimensional (3D) activity spaces that are fundamentally distinct from low-density urban environments. Hong Kong, as a typical high-density city with extensive 3D pedestrian infrastructure, represents an ideal setting to examine these relationships.

Recent advances in Global Positioning System (GPS) tracking and wearable sensors have allowed the capture of real-time environmental exposures and physiological responses in urban environments. However, in high-density cities, high-rise building clusters obstruct GPS signals, introducing positioning errors that undermine the validity of location-based assessments. Furthermore, existing studies have largely relied on pre-designed routes and discrete exposure scenarios, and little is known about minute-level variations in environmental exposures and their corresponding physiological responses during free-living movement. The effects of 3D pedestrian infrastructure on indoor and outdoor physical activity distribution also remain unquantified, and whether indoor and outdoor physical activity differentially affect health-related biomarkers remains unexamined.

To address these limitations, this thesis presents four interrelated studies integrating GPS tracking and wearable sensors measuring electrodermal activity (EDA) and heart rate variability (HRV) during free-living walking. The primary objectives are: (1) to evaluate GPS positioning accuracy and optimal buffer thresholds in high-density urban environments; (2) to examine minute-level physiological stress responses to dynamic urban environmental exposures; (3) to quantify indoor and outdoor physical activity distributions within 3D pedestrian environments and their socio-spatial patterns; and (4) to investigate the associations between indoor/outdoor physical activity and health-related biomarkers, and whether these associations vary by built environment characteristics. These findings establish a transferable GPS accuracy framework for high-density cities, reveal novel temporal patterns in physiological stress responses to urban environmental exposures, and quantify the role of 3D pedestrian infrastructure in shaping indoor and outdoor physical activity and health outcomes, providing actionable evidence for policymakers and public health practitioners to design activity-supportive urban environments.