We investigated how an internal model is generalized when the dynamics of the arm is changed during reaching movements in a force field. We also investigated whether generalization occurs in intrinsic or extrinsic coordinates. Three regions of the workspace were used to train and test the subjects: Left, Right and Center. The subjects were trained in one region with a force field and then were tested in another region with the same force field. The results show substantial generalization in reaching movements when the applied force field is in joint-based (intrinsic) coordinates.