High-speed X-ray data of sawteeth in TFR are interpreted using a Kinematic model. It is shown that the internal disruption begins for a small size of the q = 1 island, and that the sharp details observed on different chords are not reproduced by a total reconnection model. They are, however, well simulated by a model where the temperature flattening is due to the propagation of a turbulent region starting from the q = 1 surface.