## 4 Discussion
In terms of duration, the number of sessions and weekly frequency of rehabilitation programmes with commercial video games, there was variability between the studies included in this SR. Overall, the average number of sessions was nine in two studies [26; 32] or 42 sessions in another one [37]. No differences were found in the results in relation to the total duration of the intervention weeks, the number of total sessions or the weekly frequency of the sessions. On the other hand, in the majority of the studies where no difference existed in the session times of treatment between the groups, significant statistical differences were found in balance and/or gait in favour of the EG [33; 36; 39; 41; 42]. Some authors suggested that these improvements in the EG were due to patients being highly motivated and thanks to the possibility offered by these systems to constantly adapt the activities to the demands of participants. Commercial video consoles offer accessible tasks, but they are challenging and have the possibility of training skills, which cannot be performed in a natural way in real life; this motivation encourages participation and concentration during therapy [17; 18; 19; 41]. Likewise, these devices allow variable practice of repetitive tasks similar to those performed in their daily routine, which favours the efficient transfer of learning and, thus, enables the tasks to be performed in different contexts and situations, as indicated by several authors [60]. The feedback provided by these devices is also important, since auditory and visual signals inform of errors when performing the movements. Thus, the user is aware of his/her posture and movements at all times, activating brain circuits similar to those that would be activated with the same practice in real life [41; 60]. Most of the studies show the main advantages (Table 6) related to the \"active ingredients\" that make VR interventions effective in promoting recovery in stroke patients. The therapeutic advantages are related to principles relevant to neuroplasticity, such as providing goal-oriented tasks, increasing repetition and dosage, providing therapists and patients with additional feedback and allowing to adjust the task difficulty. In addition, it has been suggested that the use of VR increases patient motivation, enjoyment, and engagement; makes intensive task-relevant training more interesting and offers enriched environments. The video consoles used were different as regards the ways to interact with the systems and the virtual environments. A remote control is needed in order to use the Wii(r) console, which functions through a Bluetooth connection. Due to their upper trunk pathology, this is not something that all patients affected by stroke can do, as is seen in one of the studies included in the SR [32]. Therefore, some patients need an adaptor to be able to hold the control or a system for holding it in their hand. Good balance in bipedestations is required in order to use the Wii Balance Board(r), as the individual must remain on the board in a restricted area; thus, his/her support base is reduced and at a height of approximately three cm from the floor. This limits the possibility of using it with a