When we talk about movement-based systems we can assume that their users move. Particularly, in rehabilitation systems, patients have to perform exercises to re-train particular bodily skills through bodily activity. Many examples of those systems exist, but how we interact with them may differ, in some cases the patient performs the bodily activity through virtual environments (virtual reality), in other cases the activity could be mixed (mixed reality) or yet in another cases the activity could be through tangible interfaces, but in all of these cases, interfaces to perform bodily activity beyond mouse and keyboard are needed. Frequently interfaces use videogames to mediate the interaction between activities in the real world and activities in the virtual world; it is for this reason that we need to address questions of player experience and game design in movement-based rehabilitation systems. This paper proposes a view that takes into account aspects of user experience in the context of movement-based rehabilitation systems, focusing on concepts like immersion and flow.