## 4 Discussion
### Future Work and Clinical Applications  
Here, we focused on healthy subjects to investigate the effect of the mechanical structure of the Ekso and its different assistive modalities on muscle activity patterns during walking. The reason is that during walking, healthy subjects have highly repeatable activations both individually and as a group. Since neurological diseases and injury might affect the neural control of movements and the ability to walk differently, the muscle activations of the patients could have higher variability in both cases. However, we performed this study with the goal of understanding the changes induced by the Ekso for identifying subsets of the population that would derive higher or lower benefits from its use. For example, in this study, we found a decrease in distal muscular activity (TA, SOL, and GM muscles) during the push-off phase, in favor of greater activity in the proximal part of the lower limb, with an extra-activation at the level of the muscles' knee flexors. This suggest that subjects with ankle propulsion deficits would have limited benefits from treatment with this type of exoskeleton, since they need a specific rehabilitative training that enhances the activity of the distal muscles. Moreover, the protocol could be used to test the effects of this and other exoskeletons to provide indications on how to improve their mechanical structure or assistance. We are also starting to use the proposed protocol with SCI survivors with incomplete injury who have different gait patterns, depending on the level of injury and the type of incompleteness (e.g., ASIA (American Spinal Injury Association) classification B,C,D, [55]). In this case, we are using the proposed protocol to investigate before training the muscle activations during walking with the Ekso, aiming at characterizing the effects of the different assistance modalities to select the most appropriate combination for personalized training. Moreover, the same protocol could then be used to investigate the effects of an exoskeleton-based training on specific patients walking patterns, analyzing the changes in the muscle activities due to practice. Instead, in people with complete SCI who have no muscular activity at the level of the lower limbs, the exoskeleton has undisputed value for allowing the users to maintain the standing posture and walking, with consequences on cardiovascular health and cardiovascular training [15; 56]. In this case, while using the exoskeleton, the subjects would be actively contributing to walking with their upper body [57]. Therefore, it would be interesting to propose an evaluation protocol based on similar techniques as well as answering similar questions, but focusing on the muscular activity of the upper limbs and the trunk during walking with exoskeleton. The following are available online at [[http://www.mdpi.com/2076-3417/9/14/2868/s1](http://www.mdpi.com/2076-3417/9/14/2868/s1)]([http://www.mdpi.com/2076-3417/9/14/2868/s1](http://www.mdpi.com/2076-3417/9/14/2868/s1)), Figure S1: Comparison between normal walking and walking with walker and crutches, Table S1: Data not available for the analysis. **Author Contributions**: Conceptualization, A.D.L., S.M., C.L., L.R., S.G., A.M. and M.C. ([PERSON]); Methodology, A.D.L. and M.C. ([PERSON]); Formal Analysis, A.D.L., A.B., G.M., L.P., M.C. ([PERSON]); Investigation, A.D.L. and S.M. ; Writing-Original Draft Preparation, A.D.L., A.B., G.M., L.P., M.C. ([PERSON]) and M.C. ([PERSON]); Writing-Review & Editing, A.D.L., A.B., S.M., G.M., L.P., M.C. ([PERSON]), C.L., L.R., S.G., A.M. and ([PERSON]); Supervision, A.M. and M.C. ([PERSON]). Funding: This research was supported by the Marie Curie Integration Grant (REMAKE, FP7-PEOPLE-2012-CIG-334201), the Ministry of Science and Technology, Israel (Joint Israel-Italy lab in Biorobotics \"Artificial somatosensation for humans and humanoids\"), the Research projects of national interest (ModuLimb, PRIN-2015 HFWRY) and the PhD scholarship of Regione Liguria to [PERSON].