## 4 Discussion
The mean differences in scapular posterior tilting, at 30\({}^{\circ}\) of HT elevation, between PNF-D2 and shoulder flexion and shoulder scaption were very low (<1\({}^{\circ}\), \(p\) > 0.05). However, there was a statistically significant difference when comparing PNF-D2 with shoulder abduction (\(-\)2.1\({}^{\circ}\) (\(-\)4.1\({}^{\circ}\)--0.1\({}^{\circ}\)), \(p\) = 0.034). It is important to consider that PNF-D2 involves a combination of moving from the left side to the right side while elevating the arm above shoulder height (and vice-versa). This complex movement pattern is likely to require different muscle recruitment and coordination compared to the simpler \"left side\" and \"right side\" tasks studied by [PERSON] and [PERSON], which targeted lower than shoulder height. Therefore, the conflicting results in 3D scapular kinematics between studies are not surprising. Comparing our findings with other studies that have investigated scapular kinematics during functional tasks is even more challenging, because several factors differentiate our study. Unlike some previous studies [5; 6], we specifically examined a diagonal movement pattern of arm elevation, which is distinct from other functional tasks and has its unique scapular kinematics. Additionally, some studies did not include comparisons between constrained and functional humeral movements [7; 9], making it difficult to draw direct parallels with our results. Furthermore, in certain studies, detailed descriptions of scapular kinematics throughout the full movement were not provided [7; 8; 9], limiting our ability to make comprehensive comparisons. A recent systematic review focused on overhead athletes with and without rotator cuff tendinopathy and highlighted that the existing primary studies (comprising nine studies and a total of 332 athletes) have predominantly investigated differences and adaptations in 3D scapular kinematics during constrained arm elevation, with a particular emphasis on the scapular plane (or scaption) [3]. In the absence of a widely accepted test for evaluating functional upper extremity motion, the scaption task (involving arm elevation at an angle of 30 to 45 degrees anterior to the frontal plane) has been employed as a testing protocol to assess shoulder kinematics across various populations, including the general population and specific groups, like athletes. This choice is based on the recognition that many upper extremity activities impose arm movements that fall between the sagittal and frontal planes. However, scapular kinematics observed during shoulder scaption may not be easily extrapolated to a functional diagonal movement pattern, such as those involved in throwing motions, as demonstrated in our study. This holds true for all scapular rotations, especially those referred to as secondary or accessory scapular rotations (internal/external rotation and, to a lesser extent, anterior/posterior tilting), as well as the primary scapular rotation strongly coupled to arm elevation (upward/downward rotation). This finding holds clinical significance as variations in scapular internal/external rotation (ranging from 5.6\({}^{\circ}\) to 7.7\({}^{\circ}\)) and anterior/posterior tilting (5.2\({}^{\circ}\)) have been observed during simulated activities, like volleyball spikes among injured and non-injured players [18]. Additionally, differences in scapular internal/external rotation (ranging from 2.0\({}^{\circ}\) to 6.0\({}^{\circ}\)) have been noted between the injured and contralateral shoulder during the late cocking phase of a simulated throwing motion in baseball players [17]. Moreover, tennis players with a history of shoulder issues exhibited alterations in scapular upward/downward rotation (approximately \(5^{\circ}\)) during the late cocking position of a tennis serve compared to their non-injured counterparts [31].