Causal–Hierarchical Network of Sport-Specific Physical Fitness in Chinese Male University Tennis Athletes: Policy Insights from a Delphi–fuzzy DEMATEL–ISM Analysis

Background: Tennis is a high-intensity, intermittent sport that requires the integrated development of physical components including speed, power, agility, coordination, and endurance for competitive success. Existing physical fitness evaluation frameworks rely mainly on expert consensus and static statistical analyses. Both approaches fail to reveal the dynamic causal hierarchies and interdependencies among these components. This gap in methodology impedes the design of training intervention protocols based on systematic optimization. This study aims to (1) identify the major physical fitness components of Chinese male university tennis athletes based on a Delphi consensus process, and (2) quantify their causal hierarchy using an integrated fuzzy DEMATEL–ISM approach. Methods: The study was conducted in two phases: (1) establishment of an evaluation framework through a three-round Delphi survey of 23 experts; and (2) quantification and confirmation of the causal hierarchy among the components using a fuzzy DEMATEL–ISM approach, based on the judgments from eight experts. Results: Five primary components were identified. The fuzzy DEMATEL–ISM analysis demonstrated that coordination (cause degree = 1.94; influencing degree = 8.84) and agility (cause degree = 0.87; influencing degree = 8.89) were considered foundational drivers, speed (centrality = 17.05) and power (centrality = 17.00) as dependent hubs (negative cause degrees) and endurance (centrality = 11.31) as an independent outcome. A two-tier hierarchy was confirmed based on the ISM results, with agility and coordination driving speed, power, and endurance. Conclusion: A causal–hierarchical network of tennis-specific physical fitness was established, identifying coordination and agility as the foundational drivers. Priority should be given to these foundational drivers in training programs before targeting speed and power improvements, while endurance can be addressed independently. A novel paradigm was provided by the integrated Delphi-fuzzy DEMATEL–ISM methodology for analyzing complex athletic performance.