Buffering effects of public sports facilities on physical activity and health equity during commercial facility fluctuations: A natural experiment in Shenzhen, China

Background accessibility to physical activity (PA) facility can strongly influence population health outcomes through PA engagement duration in neighborhoods. While commercial facilities tend to spatially cluster, creating inequitable PA opportunities and health disparities between neighborhoods, little is known about how public facilities buffer against such neighborhood health inequities. Regulation of facility openings during the COVID-19 pandemic provided a natural experimental setting to examine this relationship. Methods We conducted a longitudinal study of PA behaviors among 701 residents from 23 neighborhoods in Shenzhen during facility closure and reopening (2019–2020). Using difference-in-differences (DID) analysis, we examined how different types of facilities influenced various PA duration. Through triple-difference (DDD) analysis, we investigated how public facilities moderated PA duration responses to commercial facility changes within 1,000-meter catchments. Results PA facilities showed distinct functional effects, with parks increasing light physical activity (LPA) ( β  = 39.45, p = 0.032) and public sports facilities enhancing moderate-to-vigorous physical activity (MVPA) ( β  = 39.07, p = 0.015); Commercial facilities exhibited spatial polarization with diminishing marginal returns, showing strong effects on MVPA in low-accessibility areas ( β  = 70.02, p < 0.001) but negligible impact in high-accessibility areas ; Through triple-difference analysis, we quantified the conditional buffering effect where public sports facilities effectively mitigated MVPA reduction in areas experiencing commercial facility disadvantages ( β  = 79.27, p = 0.050), with this effect being strongest in commercially deprived areas ( β  = 42.51, p = 0.001). Conclusions Through spatially balanced distribution and complementary functional design, public sports facilities effectively mitigated neighborhood MVPA inequities caused by commercial facility clustering. This conditional buffering effect was particularly significant in commercially disadvantaged areas, informing public health and urban planning policies for building resilient and equitable urban PA environments.