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

Area of Science:

• Biomechanics
• Human Movement Analysis
• Kinesiology

Background:

• The hand-behind-back (HBB) movement is a common functional task.
• Understanding the biomechanics of HBB movement is crucial for rehabilitation and sports performance.
• Previous research has not fully elucidated the interplay between scapulothoracic joint kinematics, upper trunk motion, and postural control during HBB.

Purpose of the Study:

• To investigate changes in scapulothoracic joint angles and upper trunk angles during right and left HBB movements.
• To assess postural control, specifically center of pressure (COP) displacement, during HBB.
• To identify any right-left asymmetries in these parameters during HBB movement.

Main Methods:

• Twenty healthy right-handed men performed HBB movements in a standing position.
• A three-dimensional motion capture system was used to record movement data.
• Measurements included scapulothoracic joint internal rotation, upper trunk rotation, and COP to analyze right-left differences.

Main Results:

• HBB movement elicited contralateral upper trunk rotation and ipsilateral scapulothoracic joint internal rotation.
• Lateral displacement of COP was observed on the non-HBB side.
• No significant right-left differences were found in any of the measured parameters.

Conclusions:

• Upper trunk contralateral rotation and standing postural control during HBB movement are performed symmetrically.
• These findings suggest that HBB movement integrates upper trunk motion and standing postural control.
• Scapulothoracic joint angles, upper trunk rotation, and postural control are important considerations for physical therapy evaluations and interventions involving HBB.