This paper presents a simple mechanical model capable of evaluating a running effectiveness index \(\epsilon _{EI}\) based on mechanical energy. We extended a spring-loaded inverted pendulum model, considering the biomechanical determinants of running economy (RE), to develop a simplified mechanical model that can accurately represent the \(\epsilon _{EI}\) calculated by a detailed running model. To assess the accuracy of the proposed model in estimating RE, we computed the \(\epsilon _{EI}\) using both the proposed and detailed models, based on data obtained from running experiments. A linear regression analysis using the least squares method was performed to analyze the relationship between the \(\epsilon _{EI}\) values calculated by the two models. The regression analysis results of the \(\epsilon _{EI}\) values obtained from the two models yielded significant F-statistics ( \(p < 0.01\) ) for all four participants, demonstrating that the proposed model can sufficiently represent the running economy index calculated by the detailed model.
