## 5 Conclusions  
This study demonstrates that axonal degeneration in motor fibers of lower extremity nerves, despite the absence of damage to lumbosacral neuromeres, is an inevitable secondary pathological change appearing after incomplete spinal cord injury at cervical or thoracic levels. This is likely to be caused by the lack of control from the supraspinal centers to the motoneurons below the level of damage. Pathologies in nerves make the recovery of the patient's motor abilities unattainable, even after spontaneous regeneration of spinal structures induced by intensive kinesotherapy combined with electrotherapy. The individual algorithm of nerve electrostimulation applied in this study to the patients after iSCI, designed with the objective non-invasive neurophysiological tests, supported spinal cord regeneration. Such therapy may improve the neural transmission of nerve impulses, inhibit degenerative processes in axons, and accelerate axonal regeneration. Electrotherapy also enhances muscle contractile properties, thus diminishing pathological symptoms after iSCI. The specific neuromodulatory effect of FES may reflect the improvement in motor transmission not only peripherally but also at the interneuronal and motoneuronal levels. The importance of including electrotherapy in the current standard of care has been supported by the comparison of neurophysiological data in iSCI patients treated with kinesotherapy (K group) and those treated with kinesotherapy and electrotherapy (K + E group).  
We hypothesize that the improvement of motor function needed significant afferent input provided by the kinesotherapeutic procedures applied to the patients of both groups. However, the electrotherapeutic stimulus transmitted via stimulated fibers might play a special facilitating role which influenced the effectiveness of treatment in the iSCI patients from the K + E group.  
The results of this study support the conclusion that FES may inhibit secondary degenerative changes in motor fibers, transmitting neural impulses from motoneurons to muscles in iSCI; thus, it may trigger their functional recovery. These findings contribute to the development of evidence-based therapies that promote recovery after spinal injuries.  
Conceptualization, J.H., A.W., A.S.-S., K.L., W.F. and P.T.; Investigation, J.H., A.W., W.F., S.O. and P.T.; Methodology, J.H., A.W., K.L., A.S.-S., W.F., S.O. and P.T.; Software, J.H., A.S.-S.; Validation, J.H., K.L., A.W., W.F., S.O. and P.T.; Formal analysis, J.H., K.L., A.W. and P.T.; Writing--original draft preparation, J.H., K.L. and A.W.; Writing--review and editing, J.H., K.L., A.W., W.F. and P.T.; Visualization, J.H. and K.L.; Supervision, J.H. and P.T. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Bioethics Committee from the University of Medical Sciences (decision No 559/2018). Informed Consent Statement: Informed consent was obtained from all the subjects involved in the study.  
Data Availability StatementAll the data generated or analyzed during this study are included in this published article.