# Preliminary Biomechanical Evaluation of a Novel Exoskeleton Robotic System to Assist Stair Climbing
## 5 Conclusions  
In this pilot study it could be shown that the developed eBUS assists the ascent and descent of stairs. On one hand, this is indicated by the applied knee extension moment of the eBUS and, on the other hand, by the reduced muscle activities of the knee joint extensors. However, it also became evident that exoskeletons can affect subjects individually and should, therefore, be designed or adjusted to be subject-specific. This concerns, for example, the shape of the eBUS or its settings regarding segment lengths. Since the additional mass of the eBUS leads to compensatory movement of the upper body and the kinematics are significantly changed during both movements, the mass of the eBUS should be further reduced. Since stair climbing is a comparatively slow movement with low angular velocities but large joint angles, assistance could be obtained for all three subjects. The results of this pilot study clearly show that a more individual application of force as well as an individual amount are required to provide adequate assistance. Furthermore, the goal of further optimizations of the system that is presented here should be to achieve shorter cycle times and a more cyclic movement. Since the results in this pilot study are based only on the movement patterns of the subjects and the eBUS as well as on externally measured forces, additional sEMG measurements of all relevant muscles of the lower musculoskeletal system should be performed for future studies. This would also allow for the detection of subject-specific changes in movement strategies. Furthermore, an analysis of the joint power is useful in order to find out in which phases the human has to generate or absorb energy. A study with a larger number of subjects and trials would increase the statistical power. In subsequent studies, elderly people should also be tested, since they are the actual target group of the eBUS. In any case, further studies are necessary to investigate and ideally exclude potential damage to humans by the eBUS. For this purpose, it should be investigated, in particular, whether a redistribution of joint moments takes place as well as what effects the increase in the knee joint reaction force that is determined during the ascent has on humans. All in all, it has been shown that the complex methods that are used here are suitable for evaluating the biomechanical function of exoskeletons. Other types of exoskeletons could also be evaluated with the methods that were used here. Conceptualization, J.J. and J.Z. ; methodology, M.B. ; formal analysis, M.B. and R.T.; investigation, M.B., H.-P.K. and M.W. ; resources, M.W., J.J. and J.Z. ; data curation, M.B. and H.-P.K. ; writing--original draft preparation, M.B. ; writing--review and editing, M.B., R.T., H.-P.K., J.J. and M.W. ; visualization, M.B. and R.T.; supervision, M.W., J.J. and J.Z. ; project administration, J.J. and J.Z. ; funding acquisition, J.J. and J.Z. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by Sachsische AufbauBank and the European Regional Development Fund (ERDF), grant number 3000917185. We acknowledge support by the Open Access Publication Funds of the HTWK Leipzig. **Institutional Review Board Statement:** The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of University Leipzig (approved on 05 August 2021 with protocol code 2021.07.13_eb_107). **Informed Consent Statement:** Informed consent was obtained from all subjects that were involved in the study. **Data Availability Statement:** The data that are presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy restrictions. **Acknowledgments:** We would like to thank [PERSON], who developed the control system for the exoskeleton and played a key role in the data recording.