Surface velocities of rotating stars during the first crossing of the Hertzsprung gap and at three different times of the blue loop for stars between 7 and 15 M_⊙. These four moments are indicated in the small top right inset by coloured lines and dots with corresponding colours. Left panel: equatorial velocity υ_surf. Right panel: ratio of the equatorial to the critical velocity υ_surf/υ_crit.