## 2 Materials and Methods  
### Participants and Study Design  
Figure 1 provides a visual representation of the overall design and course of this study. We recruited shooters who met the inclusion criteria and were then screened for CTS. Those who tested positive in clinical evaluation underwent a neurophysiological examination. Figure 1: Study design. The initial trial included 50 members of a local shooting club of both sexes. Before the study, the subjects were asked to confirm their history of systematic training with handguns (minimum of 6 months), and the lack of subjective symptoms (\"no subjective symptoms\") confirmed the development of pathologies in the upper extremities, such as motor and sensory impairments and cervical pain. Subjects gave written informed consent to participate in the study. Exclusion criteria included severe spinal or head trauma, history of stroke and other neurological or autoimmunityical diseases, recent pregnancy, and presence of a pacemaker or cochlear implant. Eight people declined to participate. In total, 42 patients underwent a clinical evaluation for CTS, which was negative in 29 shooters and positive in 13 shooters. We used our previous experience in neurologic examination to detect brachial plexus or thoracic outlet syndrome pathologies [10]. At this stage of recruitment, four other people refused to participate in neurophysiological tests, which were aimed at precise confirmation of impairments within the peripheral nervous system. Ethical considerations were in agreement with the Declaration of Helsinki. The approval of the Bioethics Committee of the Poznan University of Medical Sciences was also obtained (including studies on healthy people, decision No. 554/17). Data on the anthropometric characteristics and shooting practice details of nine neurophysiologically tested shooters were collected (Table 1). As a control population of subjects, we recruited a group of healthy volunteers (N = 9) that was equal to the number of shooters examined neurophysiologically. Shooters and healthy volunteers did not differ significantly in gender, age, height, weight, BMI, or dominant hand (right). They were tested with the same neurophysiological methods used on the shooters to obtain reference values of recorded parameters for comparison. Among the clinical assessment methods, we used three tests: (1) von Frey filament tactile method (vFf) (for the detection of impairment in sensory perception [12; 13; 14]), (2) Tinel-Hoffman sign (for the detection of pathology symptoms in the median nerve [15]), (3) Froment's sign (for the detection of pathology symptoms in the ulnar nerve [1]), and (4) history of CTS-specific symptoms. After obtaining at least one positive result, the shooter was referred for neuropsychological tests. The tactile method of von Frey filaments to assess sensory perception was used in three areas of the upper extremity covering different dermatomes (2 nd finger--C6-C7, 5 th finger--C8-T1, and the area above the biceps--C5). It can diagnose analgesia (score of 0), normal perception (score of 1), or hyperalgesia (score of 2). The final trial included two women and seven men, whose anthropometric characteristics are described in Table 1. Overall, they practiced for seven years on average but no less than six months, with almost five shooting sessions per month.