## 4 Discussion
This position not only mimics specific sports movements, such as blocking in football or handstand and handspring skills in gymnastics, but also aligns with common strength and conditioning exercises such as push-ups and planks [1; 25]. Given that closed kinetic chain exercises are integral to training in many sports due to the demands of the discipline, assessing shoulder sensorimotor control in the plank position, as conducted in this study, appears both relevant and insightful. While extensive research has allowed to establish the reliability and validity of lower extremity sway measurements in both clinical and biomechanical contexts [6; 7; 8; 9; 10], there is a notable scarcity of studies examining the reliability of biomechanical sway measures for the upper extremity. Consequently, this investigation provides a valuable contribution to understanding sensorimotor control in upper-limb weight-bearing tasks. [PERSON] et al. [14] evaluated upper-limb sensorimotor control in weight-bearing positions using a force plate, with the wrist and elbow locked and the lower limbs stabilized. In their study, moderate to high reliability values were found for COP length and velocity, with a SEM ranging from 6.0% to 26.5%, except for COP area, which showed lower reliability [14; 30; 31]. They reported COP length and velocity as the most reliable variables [10]. Our findings are consistent with those obtained by the mentioned authors, although we found that sway length and velocity in the medial-lateral direction were most reliable. In the present research, intra-rater reliability ranged from good to excellent; however, SEM values were slightly higher than those reported in previous studies [14]. We observed the lowest reliability and highest SEM for COP area, which has also been confirmed by other researchers [32], suggesting that COP area may not be a reliable metric for assessing sensorimotor control in the upper limb, similarly as in the case of findings for lower-limb postural control assessments. In the study by [PERSON] et al. [1], shoulder sensorimotor control was evaluated in the plank position, which is similar to the methodology used in the current study. Their findings indicated moderate to excellent reliability, with ICC values of 0.71 for COP velocity in the AP direction and ICC = 0.87 in the ML direction [1]. These values closely aligned with our results for the ML direction. In contrast, our open-eyes measurements yielded higher reliability values than those reported by [PERSON] et al. [1]. Nonetheless, they only measured inter-rater reliability with a 15 min interval between measurements, without examining test-retest reliability  
Conversely, [PERSON] et al. [4] reported excellent test-retest reliability across variables, with ICCs ranging from 0.95 to 0.97. In our study, excellent reliability was achieved for some variables, while others showed lower ICC values. This discrepancy may stem from differences in testing positions, as [PERSON] et al. [4] used prone position with upper-limb weight-bearing and lower limbs supported on a table, rather than the one-handed plank position used in this trial. Additionally, they noted that the utilized Nintendo Wii platform had poor concurrent validity and high noise sensitivity, potentially inflating their reliability values [4]. These differences may suggest that the one-handed plank position may be more clinically applicable for assessing sensorimotor control in shoulder stability. The findings achieved by [PERSON] et al. [1] indicated no significant differences between the left and right extremities for any of the measured variables, aligning with our results; that is, no side-to-side differences were observed. However, [PERSON] et al. [2] demonstrated some asymmetry in patients with unilateral shoulder instability. Their results revealed that patients with recurrent anterior instability in the dominant shoulder had increased COP length and velocity, signifying reduced stability.