Objective This research focuses on the outdoor fitness facilities within complex urban landscapes. These amenities, characterized by low construction costs, high accessibility, and flexible forms, have become crucial in dense urban areas where space constraints limit large outdoor fitness facilities. The small-scale outdoor fitness facilities often blended with urban green spaces like parks, street greenery, waterfront green corridors, and greenways. The research aims to establish an evaluation tool that accurately reflects the supply and demand response status of outdoor fitness facilities across diverse groups, thereby laying a foundation for the diagnosis and precise optimization of supply and demand issues pertaining to outdoor fitness facilities in complex built environments.

Methods To effectively pinpoint the service shortcomings of outdoor fitness facilities and provide a foundation for precise enhancement, this research modularizes the service functions of these facilities and quantifies their resilience. Based on multi-source data, the research establishes a comprehensive set of evaluation tools that can simultaneously reflect the supply and demand response status of outdoor fitness facilities for diverse groups. This approach may facilitate the analysis of the correlation between the demands of multiple user groups and the elasticity of facility services. The research takes the old urban area of Nanjing as an example to demonstrate what mentioned above.

Results The research reveals that venue type facilities demonstrate relatively high elasticity and sharing capability, with their average service capability being the highest among all facility types. The concentration of such facilities significantly enhances the demand response index of various groups in surrounding areas, making these facilities a priority for development under suitable land conditions. Although footpath type facilities have a smaller average number of service modules, they boast high capacity and can provide fundamental services to satisfy the outdoor fitness demands of residents in high-density environments. Their installation is particularly beneficial in improving the demand response level for the elderly population. These facilities can be integrated with the development of linear open spaces, such as existing urban roads and water systems, which are advantageous in low construction thresholds and costs. The research also finds that young adults, despite fewer restrictions, have a higher population ratio compared to children and the elderly. This demographic factor makes it challenging for them to attain high-level demand response, which explains why the demand response level of young adults in most neighborhoods and living areas is maintained at a moderately low level in the evaluation results. Based on the evaluation of the old urban area of Nanjing, the optimization of lots and corresponding strategies can be divided into three scenarios as follows. 1) In lots with a serious shortage of facilities and low demand response indexes for the three groups, the introduction of footpath type facilities should be prioritized to address the lack of outdoor fitness opportunities and balance various facility types to provide diverse and equitable outdoor fitness options for all age groups. 2) In lots with moderate facility accessibility but insufficient response to the demands of specific groups, the introduction of outdoor fitness facilities tailored for these groups can simultaneously enhance both the accessibility of the facilities and the fairness of service provision. 3) In lots with high facility accessibility but notably poor response to the demands of specific groups, targeted renovation and optimization of existing outdoor fitness facilities, such as replacing or adding service modules, can be employed to increase fitness opportunities for these groups in a specific manner, thereby optimizing the fairness in the distribution of fitness resources.

Conclusion This research effectively establishes a comprehensive link between the supply and demand aspects of outdoor fitness facilities, playing a pivotal role in identifying service deficiencies and facilitating precise optimization strategies. By doing so, it may contribute significantly to the planning and development of future outdoor fitness facilities in urban areas. However, it is crucial to acknowledge that the demand response index evaluation, although insightful, represents only one facet of the complex dynamics of facility allocation. To develop a more holistic and effective planning strategy, it is essential to supplement this evaluation with a range of other indicators. These should include but are not limited to factors such as accessibility, which determines how easily different groups can reach these facilities; facility quality, which affects user satisfaction and safety; scale, which ensures that facilities can accommodate the volume of users; diversity, which reflects the variety of activities that can be conducted; and environmental impact considerations, which are increasingly vital in sustainable urban development. By incorporating these additional factors, a more comprehensive and nuanced understanding of the state of facility allocation can be achieved. Ultimately, such a multi-faceted strategy will contribute to the creation of more vibrant, healthy and inclusive urban communities.