Exploring nonlinear effects of built environment on jogging behavior using random forest

Outdoor jogging is a beneficial and replicable physical activity (PA). The nonlinear effects of the built environment (BE) on jogging fitness received little attention, compared with the widely-concerned linear effects of BE on walking and cycling PA. We explore nonlinear effects at trip and origins/destinations (OD) levels in the case of Chengdu using Random Forest, based on large-scale jogging trajectory data recorded by a fitness app. The major findings include: (1) BE factors exert diverse nonlinear effects on jogging at trip and OD levels. (2) Quantity and accessibility of facilities contribute largely to model predictive power. (3) Nonlinear effects are symmetrical for O/D of jogging, unlike long-distance travel. Distance to park, distance to track, and population density show U-shaped effects on OD volume. (4) Effective ranges and thresholds in nonlinear effects vary across trip/OD levels. The findings call for environmental intervention to promote PA.