## 4 Discussion
Moreover, the improvements encourage increased engagement in recreational and social activities [76], which, in turn, promotes psychological well-being and reduces social isolation. Generally, individuals with multiple sclerosis experience enhanced functional outcomes and a higher quality of life as a result of gait improvements. In the literature, the WBV, as an alternative exercise to attenuate the gait impairments in MS, has shown conflicting results [42; 44; 46; 47; 48; 49; 51]. The heterogeneity of the results is partially due to the metrics used that are characterized by low sensitivity of the test procedure to assess the specific adaptations induced by WBV exercise on locomotion. These studies generally assessed the effect of WBV on PwMS through several functional tests (timed get-up-and-go, 6 or 3 min walking test, 10 m walk) [42; 43; 44; 46; 47; 48]. None of these investigations monitored gait changes over time by using angle-angle diagram and recording the synchronized sEMG. This means that our results cannot be directly compared with those of other studies. Our method seems appropriate to provide specific information in PwMS [13], as quantification of area, perimeter and shape of the loops provides detailed information concerning the co-joint ROM (hip-knee or knee-ankle) and co-joint coordination. In the present study, the ability to control the standing posture significantly improved over time in the different conditions (static, dynamic, open and closed eyes). Following 5 years of individualized WBV intervention, all CoP sway path parameters (total length and R/L and F/B components) showed a \(\Delta\) reduction of between 40% and 60%, thus suggesting an improved postural control. In the literature, the studies that have investigated the chronic effect of WBV exercise on postural control show conflicting data; some of them confirm the positive influence on postural control following a few weeks of WBV sessions (8-10 weeks) [46; 47; 50], whereas others did not report significant improvements [43]. Recently, [PERSON] et al. [45] reported that during the WBV intervention period, in PwMS with severe forms, the balance does not degenerate, and until six weeks after the end of WBV interventions, the balance degeneration does not seem to progress. Most of the cited studies assessed balance through scored tests used in clinical practice, such as the Berg Balance Scale (BBS) [42; 43; 50] and the standing balance test [46]. The latter methods are not be able to capture mild impairments, and their poor reliability could limit the monitoring of the disease progression [77]. The current available technology to assess the postural control uses force plates by measuring the CoP displacement during a standing position [78]. Only one study has assessed the effect of WBV training by detecting CoP displacement on force plate [45], whose results suggest that during the WBV intervention in PwMS, an increase in CoP compared to the control was not observed. In our study, we measured the body sway by using a force plate under different conditions to assess the multisensory integration ability by removing the visual analyzer (eyes closed) and the proprioceptive integration response by applying an imbalance from behind. The improvements in our study suggest better function in activities of daily living in terms of improved coordination and stability of movements, as the adaptive motor behavior is based on adequate sensory integration or processing to organize an appropriate response [79]. Functional independence and enhanced stability are positively impacted by the enhancement in postural balance, which reduces the risk of falls and enhances safety during daily activities that necessitate an upright position [80]. The quality of life of individuals with MS is positively influenced by these benefits, resulting in a decreased requirement for assistance [80]. Grip strength showed some improvements over time.