## 4 Discussion  
The aim of this paper was to investigate the effects of commercial video games as low-cost semi-immersive VR systems on balance and gait in stroke patients and to know the differences between the different devices and video games used. Previous publications have shown positive effects using immersive VR systems [14; 15; 16; 44; 45; 46] on balance and gait in different neurological conditions. However, this equipment is costly and complex to use and maintain, unlike the low-cost video game systems [19] included in the papers contemplated in this SR.  
As regards the studies included in this SR, the results generally show positive effects on balance and gait in post-stroke patients. Specifically, in relation to the participants, they possess homogeneous characteristics regarding age, gender and type of stroke. On the contrary, homogeneity is not observed in progression times, including participants in chronic and subacute states. However, differences have not been observed in the results as regards to patient age and progression times, contrary to what was described in previous studies as regards the benefits of physical therapy after stroke, which showed that the oldest patients obtained lower levels of improvement and, also, that patients with the most mild condition recuperated more favourably [47; 48]. However, effect size and time x group interaction were included in almost none of the papers analysed in this SR. The assessment tools used to quantify the effects of therapy on balance and gait were heterogeneous in the studies included, which evidences a lack of standardisation in the assessment protocols of balance and gait in post-stroke patients. In several papers, objective tools were used, such as computerised dynamic posturography systems, which are considered to be baseline instrumentation methods for assessing balance [49; 50] and, in other cases, observational functional assessment tests, such as TUG or BBS, which, although amply validated in this clinical context [51; 52; 53; 54; 55], knowing how to apply them depends on the examiner's experience. Moreover, in this last test, the floor ceiling effect is frequent, which means it is not sensitive to discreet changes in patients with mild or very severe balance disorders [53; 55]. Results from all the studies show improvements in some of the aspects analysed, regardless of the approach (with or without commercial video games) that is to say, performing rehabilitation leads to improvements in patients who have suffered a stroke, which is in-line with previous reviews [56; 57; 58]. However, specifically regarding balance, no changes occurred in several of the papers included in this SR [27; 39; 40; 42] or after conventional physiotherapy treatment or when the latter was applied in conjunction with exercises in a virtual environment. However, improvements in balance during functional tasks were observed. This could be due to the fact that such tasks allow greater adaptation as regards the support base, as well as the need to perform weight transfers in a more dynamic way, facilitating postural stability, whereas maintaining bipedestations in the tests used for assessment means the support base must be kept constant, as well as the load and support points when straightening up. The results observed also seem to be linked to the length of the therapy sessions. In six studies, the session times were longer in the EG compared to the CG [25; 27; 31; 32; 35; 37]. In one of the studies, this aspect did not lead to significant differences in the results obtained for both groups [25], in contrast with the other five studies, which showed differences between the groups (in favour of the EG) [27; 31; 32; 35; 37]. Thus, there does seem to be a relationship between the length of time of treatment and the results, as suggested in previous studies as regards the effects of physiotherapy treatment on strokes [48; 59].