In this research, we have tried to analyze a training course on ICT integration and to assess the impact of such training on future teachers. We have identified the role of different types of knowledge that must be taken into account in the design of a training on the integration of new technologies in mathematics education. The impact of the teacher training concerned by the study is related to proof problems in geometry and to the design of situations allowing students to overcome proof difficulties thanks to the appropriate use of the tools of the dynamic geometry environment Cabri-Geometry.