Date of Award

January 2020

Degree Type

Open Access Thesis

Document Type

Master Thesis

Degree Name

Master of Science (MS)

Department

Exercise and Sport Science

First Advisor

Aaron D. Sciascia

Department Affiliation

Exercise and Sport Science

Second Advisor

Matthew J. Sabin

Department Affiliation

Exercise and Sport Science

Third Advisor

Tracy Spigelman

Department Affiliation

Exercise and Sport Science

Abstract

The kinetic chain plays a large role in the force production of the body during activity. The core and the scapula are critical kinetic chain links to the upper extremity during overhead motions and should likely be accounted for when performing manual muscle testing of the shoulder. The purpose of this study was to manual muscle test the shoulder with a handheld dynamometer to determine the impact of scapular positioning, core activation, and the effect of the kinetic chain on force production. Forty (40) National Collegiate Athletic Association Division I athletes (23 females, 17 male) were tested in shoulder flexion and abduction in their relative posture, with the scapula retracted, and with the core activated. There were no significant differences within or between the three manual muscle testing conditions for shoulder flexion. Relative posture (15.8±5.0kg) and core activation (15.6±5.2kg) resulted in significantly greater force generation compared to the scapula retracted position (14.7±4.5kg) on the dominant arm for abduction (p≤0.05). Relative posture (16.6±5.8kg) and core activation (16.0±5.8kg) for abduction on the non-dominant arm resulted in significantly greater force generation than scapular retraction for the dominant arm (14.7±4.7kg) and non-dominant arm (15.0±5.0kg, p≤0.045). For the female subjects, abduction in relative posture (13.8±2.8kg) resulted in significantly greater force generation compared to the scapula retracted position (12.6±2.6kg) on the dominant arm (p=0.038). For male subjects, non-dominant arm abduction in relative posture (20.5±6.7kg) and core activation (19.8±6.7kg) resulted in significantly greater force generation than scapular retraction (17.4±5.5kg) for both arms (17.9±6.0kg, p≤0.018). However, while the differences were statistically significant, the effect sizes were so small that the results may not be clinically significant. This suggests that full active scapular retraction or core activation may not aid force generation during shoulder flexion or abduction in high-level collegiate athletes.

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