Top panel: evolution of Ṗ/P, where P is the rotation period, for stellar models with various initial masses, metallicities, rotations, and surface magnetic fields. The light shaded area shows the range of values for the braking timescale as deduced by Townsend et al. (2010). Bottom panel: evolutionary tracks for stellar models with various initial masses, metallicities, rotations, and surface magnetic fields. Three black dashed lines indicate the isochrones with ages ranging from 10 to 30 Myr. The position of σ Ori E is indicated.