Date of Award

1-1-2013

Document Type

Open Access Dissertation

Department

Exercise Science

First Advisor

Paul F Beattie

Abstract

Posterior shoulder tightness is a common physical impairment in overhand baseball athletes presenting with injury. The etiology of this physical impairment is poorly understood and theorized to be a combination of bony, muscular, and inert soft-tissue contributions occurring at the glenohumeral joint. The ability to discriminate between each tissue's influences on shoulder range of motion is often challenging to overcome within a clinical environment. Chapter 2 of this manuscript provides a thorough review of the literature discussing the potential mechanisms of posterior shoulder tightness. Previous studies have independently accounted for the relationships between posterior shoulder tightness, and the mechanical contributions of bony anatomy and capsuloligamentous stability. Chapter 3 of this dissertation research is a clinical commentary that discusses the current uses of rehabilitative shoulder ultrasound imaging including specific functions to account for the theorized mechanisms of posterior shoulder tightness.

DISS_para>In overhead throwing athletes, the range of motion deficits of posterior shoulder tightness have been linked to increased prospective injury risk. Therapeutic treatment interventions have shown a promising ability to improve some of these motion deficits although programs are often not tailored to target specific tissues. Chapter 4 is a randomized controlled trial comparing the acute treatment effectiveness of a muscle-directed manual therapy intervention and posterior shoulder stretching routine versus stretching alone. The results indicate that the added use of muscle-directed manual therapy significantly enhances the amount of ROM gained when compared to stretching alone. These clinical data suggest that musculotendinous stiffness influences the deficits associated with posterior shoulder tightness.

In Chapter 5, we specifically examine the local physiologic contributions of humeral morphology, glenohumeral joint translation, and rotator cuff stiffness with the resolution of posterior shoulder tightness. Of these potential mechanisms, rotator cuff stiffness was the only tissue responsive to the application of muscle-directed manual therapy. Furthermore, the decreases observed in muscle stiffness were concurrent with the supplemental gains in shoulder ROM. These findings indicate that manual therapy treatment directly applied to the rotator cuff is effective at decreasing muscle stiffness and reducing deficits in posterior shoulder tightness.

The results of this dissertation research suggest that rotator cuff stiffness is partially responsible for the presence of posterior shoulder tightness and that muscle-directed manual therapy is effective at decreasing dominant sided deficits in shoulder ROM. Further research is required to determine the potential long-term effects of muscle-directed manual and stretching for the injury prevention and treatment of athletes with posterior shoulder tightness.

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