Laser Doppler anemometry has been applied to a bubble column equipped successively with three different gas distributors: a single-orifice nozzle, a multiple-orifice sparger and a porous plate. Axial and tangential mean and rms liquid velocity values have been measured up to a gas hold-up of 15-20%. A simple analytical model based on a bubble-induced turbulence is shown to be consistent with the results obtained with the three spargers and is used to estimate the Reynolds shear stress. The evolution of the local hydrodynamic parameters of the liquid phase with U-G is explained and related to the hydrodynamic regime, the uniformity of the gas distribution and the start-up procedure.