## 4 Discussion
### Scapulothoracic Motion, Scapulohumeral Rhythm, and Movement Quality Data  
During shoulder elevation and lowering in the frontal plane, no significant differences were found in scapular motion and scapulohumeral rhythm, despite the identified scapular muscular adaptations and the reported scapular dyskines types within the study sample. While changes in muscular coordination/balance were previously suggested as potential contributors to alterations in scapular kinematics [83], the fact that all the symptomatic subjects presented scapular dyskines compared to less than half of the asymptomatic group also led to the anticipation of differences between groups. Therefore, in the present study, the variable used to express the entire range of scapula motion in each movement/task phase does not seem to detect differences that could be restricted to a specific range of motion or that the moderate pain intensity (\(\approx\)5.6 out of 10) [52] and low impact on shoulder function (\(\approx\)31.5 out of 100) [84; 85] experienced by the symptomatic group may not have had a significant impact on overall scapular kinematics [43]. Thus, the results of the present study suggested a similar range of scapular motion between both groups. When these results are considered alongside changes in the muscular activity and ratios, which appear to indicate a negative neuromuscular adaptation [86], they suggested that the symptomatic group expends more energy [87] to achieve the same range of motion [86]. Previous studies comparing the scapular kinematics between asymptomatic and symptomatic subjects with shoulder pain have also report a lack of differences in some scapular movements, such as upward rotation and internal rotation [88].  
During the drinking task, changes in scapular motion were found. Specifically, during the drinking phase, when subjects took a \(\mathrm{sip}\) of water, a higher degree of scapular winging was observed in the symptomatic group. This finding seemed to be supported by the decreased activity of the SAlow during this phase and a compensatory increased activity of the MT. Conversely, during the backward transport phase, increased scapular upward rotation and decreased winging were observed. During this phase, the symptomatic group appeared to perform the expected scapular movement during shoulder elevation [2; 3; 4; 6; 14] but to an excessive degree compared to asymptomatic subjects. Consequently, as mentioned before, the symptomatic group seemed to expend more energy during the task. Particularly, considering the winging motion, the decrease in its range observed in this phase could be a compensatory mechanism for its increase during the drinking phase. In turn, the higher upward rotation could be a strategy to achieve the required shoulder range of motion [26] and/or to manage pain. Previous studies have often highlighted a decrease in upward rotation during shoulder elevation [17; 38]; however, other authors also reported an increase in this motion, proposing it as a compensation for shoulder weakness, joint stiffness, and pain avoidance [89]. Although the findings of the present study were statistically significant,they appear small when compared to the intra-rater minimal detectable change values reported by a previous study during the assessment of scapular protraction/retraction, tilt, or medial/lateral rotation with inertial sensors [90]. However, it is noteworthy that the mentioned study did not include scapular winging or upward rotation, which may limit the comparison.  
Previous studies have reported changes in movement quality between healthy subjects and those with neurological conditions involving the upper limb [34; 91; 92]. However, in the present study, which, to our knowledge, is the first to assess these variables in chronic shoulder pain resulting from musculoskeletal conditions, differences between groups were not found for any of the assessed parameters related to goal-directed/coordination of movements [44], temporal and performance efficiency, or even movement planning [34; 45; 91].