Effect of Flexibility Deficit on Scapular Asymmetry in Individuals with and Without Shoulder Pain

Background: Many studies have investigated the relationship between soft tissue tightness and shoulder kinematics. However, there is a lack of information on the dynamic properties responsible for side-to-side differences such as scapular asymmetry.

Objective: To determine the relationship between a deficit in soft tissue flexibility and scapular asymmetry.

Methods: A total of 58 individuals (29 patients with shoulder pain and 29 asymptomatic participants) were enrolled. Bilateral shortening of the pectoralis minor muscle and posterior shoulder tightness were assessed. Additionally, side-to-side flexibility deficit was calculated. Scapular kinematics were measured with an electromagnetic tracking device while individuals were standing in a resting position and during arm elevation. The symmetry angle was calculated to quantify scapular asymmetry.

Results: The pectoralis minor and the posterior capsule flexibility deficit showed a significant positive relationship with the symmetry angle in the resting position separately for both asymptomatic (r=0.47, r=0.37 relatively) and symptomatic groups (r=0.58, r=0.38 relatively), indicating that the increased deficit in the pectoralis minor and posterior capsule flexibility were associated with increased scapular asymmetry. However, no significant relationship was found between flexibility deficit and scapular asymmetry during arm elevation and lowering for both asymptomatic and symptomatic groups.

Conclusion: The findings of the study provided information on the relationship of a flexibility deficit on the scapular position and orientation in asymptomatic and symptomatic populations.