Modelling physical activity is a recent research topic in the field of user modelling. In our research, we aim to model complex activities such as those required to master the practice of a martial art. In particular, in this paper we present the system MyShikko, aimed to provide a personalized multisensorial support when practicing knee walking, a movement in Aikido martial art that requires keeping the body center aligned when moving the knees on the floor. The motion information for the modelling is collected from a pair of webcams in a stereoscopic configuration and the inertial sensors of a smartphone.