## 4 Discussion
In this study, both groups underwent the same scapular stabilization exercises, including strengthening exercises and postural correction (wall slide exercises), to return the overly internally rotated scapula to its retracted position. This aimed to increase the pain threshold of the infraspinatus muscle, the posterior deltoid muscle, and the teres major muscle in both groups before and after the experiment. The results of this study indicate no differences between the two groups. Possible reasons for this include the subjects not selecting the pain-related options during their choices, which resulted in a limited amount of change. Secondly, the three muscles measured were those that cause problems due to scapular internal rotation, and breath training, along with thoracic exercises, are likely to have less of an impact on these muscles. In comparison, scapular stabilization exercises have a greater impact on these muscles. This study showed that respiratory function and lower chest expansion were increased in both groups before and after exercise. Subjects with UCS experience excessive anterior tilt and downward rotation of the scapula. Exercises that stretch the chest muscles and strengthen the shoulder muscles are known to reduce poor shoulder posture, such as stretching of the pectoralis minor muscles. This can reduce excessive anterior tilt of the scapula and improve chest mobility, thereby increasing breathing muscle strength [32; 33]. A previous study reported that the aberrant structure of the cervical and thoracic spine induces a movement disorder in the rib cage, thereby impacting respiratory function and resulting in reduced lung volume, vital capacity, and weakened respiratory muscles. The integration of scapular stabilization exercises with thoracic extension exercises enhances posture and respiratory function [18]. The serratus anterior and pectoralis minor muscles serve as accessory inspiratory muscles to assist breathing [17]. In the present study, both groups initially performed the same scapular stabilization exercises, which included strengthening exercises and stretching of the pectoralis minor muscles. These exercises contributed to improving respiratory function. Based on current knowledge, diaphragmatic breathing exercises, as well as volume and flow-directed incentive spirometry techniques, have demonstrated efficacy in improving lung function [28]. In addition to the observed improvements in pain, the effects of the exercise intervention may also be attributed to underlying physiological mechanisms. Specifically, respiratory function may play a key role in managing UCS. Individuals with UCS often exhibit dysfunctional breathing patterns, such as upper chest breathing, which can increase tension in the accessory respiratory muscles, including the sternocleidomastoid and upper trapezius [34; 35]. Targeted exercises may promote diaphragmatic breathing, reduce overactivity in these muscles, and enhance oxygen delivery, thereby contributing to improved postural control and reduced muscle strain. The SBG group underwent direct breathing training, including inspiratory exercises, rib expansion exercises, and diaphragmatic breathing exercises, which contributed to improving respiratory function and lower chest expansion. In the STG group, before the correction exercise, we first had the participants stretch their rectus abdominis muscles. During the stretching process, the subjects were asked to cooperate with abdominal breathing. Postural correction exercises, posture exercises, thoracic exercises, and backward rocking exercises were performed to reduce the structural abnormalities of the thoracic vertebrae and improve the thoracic alignment. As a result, lung function improved when the thoracic alignment was corrected, further opening the chest and enhancing the expansion of the lower chest.