Top panel: The sample of 31 fast-rotating stars (blue dots) represented in the HR diagram shows the apparent T_eff and log L/L_⊙. parameters. Bottom panel: HR diagram for the same sample, assuming PNRC parameters obtained with the classical von Zeipel model. Black dashed lines represent isochrones with 10⁷ and 10⁸ yr; coloured continuum lines represent evolutionary tracks from 2 M/M_⊙ up to 20 M/M_⊙. The evolutionary tracks and isochrones were calculated by Schaller et al. (1992) supposing static (non-rotating) internal structure equations.