  We investigate a Bose Einstein condensate held in a 1D optical lattice whose
phase undergoes a fast oscillation using a statistical analysis. The averaged
potential experienced by the atoms boils down to a periodic potential having
the same spatial period but with a renormalized depth. However, the atomic
dynamics also contains a \emph{micromotion} whose main features are revealed by
a Kolmorogov-Smirnov analysis of the experimental momentum distributions. We
furthermore discuss the impact of the micromotion on a quench process
corresponding to a proper sudden change of the driving amplitude which reverses
the curvature of the averaged potential.
