Date of Award

2019

Degree Name

Exercise Science

College

College of Health Professions

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Mark Timmons, Committee Chairperson

Second Advisor

Dr. William Garrett

Third Advisor

Dr. Joseph Beckett

Abstract

Background: Shoulder pain is a common occurrence in the general population. Pain has been associated with shoulder impairments and pathology. Associations between shoulder limitations, impairments, and mechanisms of injury and altered scapular motion appear in the literature. Fatigue of the scapular stabilizing muscles resulting from repeated arm motion has been reported to alter scapular kinematics, which could result in shoulder pathology, especially impingement.

Purpose: The purpose of this study was to examine the effects of fatigue of the serratus anterior muscle on scapular kinematics. The hypotheses were that there would be decreased posterior tilt and decreased upward rotation during arm elevation after selective fatigue of the serratus anterior.

Methods: Thirty participants (20 females, 10 males) were included in the investigation. Scapular kinematics and shoulder strength were measured prior to and immediately following a serratus anterior fatigue protocol. A two factor (Fatigue x arm elevation angle) repeated measures ANOVA was used to determine the effects of serratus anterior fatigue on scapular kinematics.

Results: There was no statistical significance in upward rotation of the scapula between pre- and post-fatigue conditions (ascending: p=0.188; descending: F p=0.798). Less scapular posterior tilt was found following the fatigue protocol between 60° - 90° and between 90° - 120° of arm elevation, during the ascent (p=0.004) and the descent (p=0.013). A statistical significance of fatigue by arm elevation angle was also found for clavicular elevation during the ascent (p=0.050) between 90° - 120° of arm elevation. A statistical significance of fatigue on internal rotation was found during the ascent (p=0.027). There was no statistical significance in clavicular protraction between pre- and post-fatigue conditions (ascending: F p=<0.001; descending: F p=<0.001).

Conclusions and Practical Relevance: Fatigue of the serratus anterior resulted in decreased scapular posterior tilt, and greater clavicular elevation at higher arm elevation angles along with greater scapular internal rotation. These findings are consistent with the scapular kinematic patterns associated with shoulder pain. Improving the endurance of the serratus anterior might reduce the scapular kinematics associated with mechanism of injury for the shoulder complex.

Subject(s)

Kinematics.

Dynamics, Rigid.

Shoulder joint -- Physiology.

Shoulder pain -- Treatment.

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