Objective Due to the advancement of urbanization in China, a series of severe public health problems have ensued, and chronic diseases have become one of the major diseases that cause death among urban residents. Green space in urban parks has various functions, such as reducing air pollution, regulating temperature and humidity, and mitigating noise, which can provide residents with ideal and comfortable places for physical activity. However, previous research on promoting physical activity in urban parks primarily focuses on the correlation between park characteristics and physical activity behavior, typically concentrating on single-dimensional characteristic measurement. The research on direct correlation between park green space characteristics and physical activity ignores the complexity of the action pathways between them. Therefore, constructing a multi-dimensional assessment system of park green space characteristics and clarifying the action pathway between green space and physical activity have both theoretical value and practical support for urban green space planning and layout oriented at health behavior.

Methods This research takes two sample plots in Nanjing with significant differences in greenness level indicators as research objects (Xiamafang Park and Yanziji Park), recruits 56 subjects to participate in a 2-hour free physical activity experiment, records the type and duration of the activity, measures the real-time data on park green space characteristics in the sample plots, and finally models and analyzes all the data from each spatial unit of the physical activity. Specifically, the park green space characteristic system is divided into two-dimensional spatial characteristics and three-dimensional visual characteristics. The two-dimensional spatial characteristics include usability characteristics (NDVI), organizational characteristics (connectivity value, and integration degree), and accessibility characteristics (distance from the network of entrances and exits, and vertical distance from external roads), and the three-dimensional visual characteristics are the visibility characteristics (green visibility, and canopy density). Secondly, the partial least squares structural equation modeling (PLS-SEM) is utilized to link the multidimensional park green space characteristics with physical activity representations and to clarify the potential influence pathways between park green space characteristics and physical activity, with park green space characteristics as the independent variable, physical activity characteristics as the dependent variable, and noise, temperature and humidity index, and air pollution as the mediator variables. Finally, based on the mechanism of “park green space – physical activity” under different levels of greenness, the research explores the methods and optimization approaches for promoting physical activity by urban park green space planning.

Results This research finds that the correlation between the multi-dimensional park green space characteristic indicators may be affected by the level of greenness of the green space, the two-dimensional indicators of usability characteristics (NDVI), and the three-dimensional indicators of visibility characteristics (green visibility, and canopy density) in the green space with high greenness show a significant positive correlation; in the green space with low greenness, the environmental organization characteristics and the accessibility characteristics positively affect noise perception and thus positively promote physical activity; the microclimate comfort is the most critical mediator variable in the green space affecting physical activity, which cannot be affected by the difference in the greenness of sample plots.

Conclusion The findings of this research provide empirical evidence that park green space characteristics influence physical activity behavior through environmental stressors, and the differences and similarities in pathways between park green space characteristics and physical activity are analyzed in relation to different green spaces. First, an indicator system coupling two-dimensional spatial characteristics and three-dimensional visual characteristics is investigated to provide a more scientific and comprehensive method for assessing park green space characteristics. Second, the temperature and humidity index in the parallel mediation model is shown to be a more critical pathway, indicating that microclimate comfort greatly influences the physical activity representations of the active population. The guidance and shaping of green space need to fully consider the composite perception of the crowd on green visibility, canopy density, and microclimate, and the environmental optimization of green space should pay attention to the moderate principle in terms of green visibility. Third, there is a significant positive correlation between noise and the frequency of physical activity in urban green space, and noise feeds back to the attractive characteristics of green space. Fourth, the convergence of people may increase the frequency of staying and passing through a green space. Finally, the research results may provide ideas for subsequent investigation of the association mechanism between green space and physical activity in urban parks and provide strategies for health-oriented urban green space planning and design.