## 1 Introduction  
Effective sensorimotor control of the shoulder is crucial for stabilizing the upper extremity and maintaining postural stability [1; 2]. However, shoulder pain and dysfunction are common issues within the athletic population [3; 4]. Injuries affecting stabilizing structures of the shoulder can impair sensory and proprioceptive feedback, delay neuromuscular responses, and disrupt central integration, which collectively compromise sensorimotor control [3; 5]. Given these potential impairments, evaluating upper extremity function in weight-bearing positions is essential to better understand and address alterations in shoulder sensorimotor control [4]. Although assessments in weight-bearing positions are well-documented for the lower extremity [6; 7; 8; 9; 10], research focused on similar evaluations for the upper extremity remains limited. Due to the limited number of studies conducted in this area, some of the supporting research cited in this work is older than five years; however, referencing these older studies is essential, as more recent data are unavailable. In the literature, it is suggested that measuring the center of pressure (COP) may help identify sensorimotor deficits, particularly in athletes (e.g., swimmers) and patients undergoing surgical treatment for shoulder joint issues [3; 8]. Monitoring COP sway on a force platform in weight-bearing positions for the upper limbs provides a precise evaluation of shoulder sensorimotor control by capturing subtle deficits in proprioception, balance, and neuromuscular coordination [11]. This approach is particularly relevant in diagnosing and managing rotator cuff pathologies, where impaired sensorimotor control often contributes to pain, instability, and functional limitations [2; 12]. Incorporating the sway test into rehabilitation protocols can offer a quantifiable measure of proprioceptive deficits and motor control recovery, enabling personalized therapy adjustments. Moreover, using COP analysis as part of pre-surgical assessment may help clinicians identify individuals at higher risk of poor surgical outcomes, guiding decision-making in both conservative and surgical management strategies. Thus, the application of this method may be a valuable tool in both optimizing rehabilitation outcomes and enhancing pre-surgical planning. In extensive research, sway and postural stability measures have been explored for the lower limbs, demonstrating reliability levels that range from poor to excellent [6; 7; 8; 9; 10]. However, upper limb balance has only been examined on a force platform in a few studies, highlighting an area that warrants further investigation [1; 2; 13]. [PERSON] et al. [2] proposed using a force platform as a feasible and reliable approach for assessing shoulder sensorimotor control. They conducted assessment with the upper limbs in weight-bearing positions while the lower limbs rested on a table to the anterior superior iliac spines [14]. [PERSON] et al. [11] examined the sensorimotor function of the shoulder by analyzing COP movement on a force plate during a one-handed support task in supine position. They proposed that individuals undergoing surgical stabilization of the acromio clavicular joint would exhibit lower sensorimotor function in the operated shoulder compared to the contralateral, healthy side, despite achieving positive clinical and functional outcomes [11]. However, they noted that in control subjects, there were no discernible side-to-side differences in stabilometric parameters [11]. Furthermore, [PERSON] et al. [15] reported that athletes with impingement syndrome displayed diminished static and dynamic stability in the affected shoulder compared to the contralateral shoulder and the healthy control group. They observed a significant decrease in the static stability of the shoulder in conditions where the eyes were closed, indicating a potential reduction in sensorimotor control attributed to a proprioceptive deficit [9; 10; 15].