Most massive galaxies have grown their sizes during cosmic time. Several mechanisms have been proposed to explain this growth, being minor mergers the most promising way. The key feature of this mechanism is that it can reproduce in a very efficient way the observed size growth. The number of satellites around the massive galaxies has also been used to support observationally minor-merging mechanism; however, this evidence has a big uncertainty because a merger time scale needs to be assumed. In this poster we will use velocity dispersion measurements at high redshift as an opportunity to explore the structural properties of massive galaxies. This will allow us to constrain the different evolutionary mechanisms, and in particular to check whether minor mergers remain as the most favoured growth channel.