Trunk rotation and scapular muscle activity and kinematics
Recent studies have shown that exercises loading the kinetic chain (by extending the trunk and hip) facilitate activity in the scapular muscles. This study investigated whether ipsilateral trunk rotation elicited similar effects. It was found that scapular external rotation and posterior tilt increased, that lower trapezius activation increased and upper trapezius activation decreased in the presence of ipsilateral trunk rotation.
In the past decade, exercises targeting the scapular muscles have become an integral part of the shoulder rehabilitation. Proper activation of the force couples formed by upper, middle and lower trapezius (UT, MT and LT, respectively) and serratus anterior (SA) increases scapular upward and external rotation and posterior tilt. It has also been shown that implementing a diagonal movement pattern (e.g. contralateral hip extension) facilitates scapular muscle activation.
The current study investigated whether an ipsilaterally rotated trunk position has similar effects. For this purpose, thirteen asymptomatic men performed six exercises (scaption, external rotation, external rotation in 90 degrees of abduction and prone retraction in 45, 90 and 145 degrees of abduction) with and without ipsilateral trunk rotation while kinematic data and EMG were collected.
In exercises that were performed in the upright position (i.e. scaption and both external rotation exercises), ipsilateral trunk rotation led to increased LT activation and increased scapular external rotation and posterior tilt. In the exercises during which the subjects lay prone, UT activation increased, thereby positively influencing (decreasing) UT/MT and UT/LT ratios.
Do you incorporate exercises loading the kinetic chain in your rehabilitation? Which ones do you use, and why?
> From: Yamauchi et al., J Shoulder Elbow Surg 24 (2015) 955-964. All rights reserved to the Journal of Shoulder and Elbow Surgery Board of Trustees. Click here for the Pubmed summary.