  Recent stellar evolution computations show that the blue supergiant (BSG)
stars could come from two distinct populations: a first group arising from
massive stars that just left the main sequence (MS) and are crossing the
Hertzsprung-Russell diagram (HRD) towards the red supergiant (RSG) branch, and
a second group coming from stars that have lost considerable amount of mass
during the RSG stage and are crossing the HRD for a second time towards the
blue region. Due to very different luminosity-to- mass ratio, only stars from
the second group are expected to have excited pulsations observable at the
surface. In a previous work, we have shown that our models were able to
reproduce the pulsational properties of BSGs. However, these models failed to
reproduce the surface chemical composition of stars evolving back from a RSG
phase. In this paper, we show how the use of the Ledoux criterion instead of
the Schwarzschild one for convection allows to significantly improve the
agreement with the observed chemical composition, while keeping the agreement
with the pulsation periods. This gives some support to the Ledoux criterion.
