## 2 Materials and Methods
### Participants
#### 2.1.1 Athletes  
Sports clubs competing in the Portuguese Men's Volleyball Elite League and the Portuguese Men's Volleyball National Team (Portuguese Volleyball Federation) were contacted via telephone and e-mail (mostly coaches and/or managers), previously during seasons 2018-2019 and 2019-2020, to disseminate study objectives and procedures, obtain clearance to use their facilities for data collection, and assist in athletes' recruitment. A flyer, either in physical and/or digital format, explaining study objectives and procedures, including a frequently asked questions section for athletes, was distributed. Eligibility to participate was (a) being 18 or older, (b) perform at least 150 degrees of arm elevation, and (c) being involved in competitive indoor volleyball in the past 2 years. Exclusion criteria for this study was (a) history of shoulder dislocation, (b) upper extremity (UE) surgery in the past 6 months, (c) UE injury in the past month, (d) UE pain at the time of testing, including pain in cervical and thoracic spines or pain in the upper body quadrant triggered by cervical or thoracic spine mobility tests, (e) self-perceived limitation to fully participate in vigorous activities or competing sports (score 5 on any of the items of the Portuguese version of the Disabilities of the Arm, Shoulder, and Hand (QuickDASH)--sports module [23]), (f) evident abnormalities/deformities in the musculoskeletal spinal, rib cage and shoulder girdle structures (e.g., hyper-kyphesis, scoliosis, pectorus excavation, atrophy of infraspinatus muscle), and (g) lower extremity length inequality (\(\geq\)1.5 cm).  
Following the preliminary contact with Portuguese clubs and the national team, researchers went to sports organizations to perform a structured interview and physical examination and collect biomechanical data on athletes willing to participate. Further participation was asked individually in situ. The structured interview included a detailed questionnaire assessing the duration of sports participation, amount of weekly training and competition activity, possible episodes of shoulder, elbow or wrist pain and injury or surgery, and current status of self-perceived physical performance and limitations to participate in sports (QuickDASH--sports module, Portuguese version; internal consistency, \(\alpha\) Chronbach = 0.95; test-retest reliability, intraclass correlation coefficient (ICC) = 0.886), including shoulder/upper extremity pain (body chart mapping, 0-10 pain rating scales), weakness or fatigue, and instability (0-10 rating scales) [24; 25; 26]. Physical examination consisted of, but was not limited to, anthropometrics (e.g., height, weight), and standard clinical inspection of postural alignment and mobility of the upper body quadrant, including neurological examination of muscle power (myotomes) plus external/internal shoulder rotator muscles (manual muscle testing). Performance of scapular position and motion was assessed using the scapular Dysokines Test (SDT), according to [PERSON] et al. [27]. Athletes were rated as having normal, subtle, or obvious abnormal scapular motion patterns during bilateral arm elevation in the sagittal (flexion) and frontal planes (abduction) while holding a 1 or 2 Kg dumbbell (self-selected by participants) in their hands. This method has demonstrated satisfactory reliability for clinical use in overhead athletes (percentage of agreement, 75-82%; weighted kappa coefficients, 0.48-0.61). The first author, an academic musculoskeletal physiotherapist, conducted all interviews and physical examinations.