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This abstract aims to present the assessment of a new dimensionless number for the study of dynamic similarity (DS) during running by using a computer simulation. Previous studies on walking (Bisiaux et al., 2003, Moretto et al., 2007) induced DS between subjects and reported a decrease of data variability by using the Froude number, a dimensionless number founded on mechanical energy transfers occurring during walking. Delattre et al. (2007) reported that the use of the Strouhal number (another dimensionless number based on the spring-mass model (SMM) for the mechanics of running) enabled to induce DS between running subjects. However it seems to us that this approach could be refined. As it has been made to highlight Nfr from the inverted pendulum model, we proposed to consider mechanical energy transfers occurring at the centre of gravity of a simulated SMM. We built two different-sized and proportional SMM, and computed EP (potential energy), EK (kinetic energy), EE (elastic energy). Results showed that the ratio R=(EP+EK)/EE was constant and reached identical value for both SMM (4.1±0.72 and 4.1±0.71) from 30 to 70% of the simulation time. Taking the limits of the simulation into account, we conclude that the dimensionless number R could theoretically be used to induce DS during running. Future investigation has to assess R for DS in vivo. [ABSTRACT FROM AUTHOR]