Changes in scapular and trunk angles and postural control during right-left hand-behind-back movement

[Purpose] This study aimed to clarify the changes in the scapulothoracic joint and upper trunk angles and postural control during right-left hand-behind-back (HBB) movement. [Participants and Methods] The participants were 20 healthy right-handed men. We measured the HBB movement while standing using a three-dimensional motion capture system. Changes in the internal rotation angle of the scapulothoracic joint, upper trunk rotation angle, and center of pressure (COP) were examined to assess potential right-left differences between the analyzed positions. [Results] As the thumb touched the buttocks, upper trunk contralateral and scapulothoracic joint internal rotations were observed and the COP on the non-HBB side was significantly displaced laterally. There were no right-left differences in the changes between the analyzed positions for all measures. [Conclusion] Upper trunk contralateral rotation and postural control were conducted without right-left differences during HBB movement. These results suggest that upper trunk movement and standing postural control are involved in HBB movement. Therefore, it is useful to focus on the scapulothoracic joint angle, upper trunk rotation angle, and standing postural control during physical therapy evaluation and treatment with HBB movement.