Date of Award

2021

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. Gary McIlvain

Third Advisor

LTC Bret Bemis

Fourth Advisor

MSG Brook Bailey

Abstract

Background: The increasing rate of shoulder pain and injury in the US military can cause an impact on a soldier’s ability to pass their fitness tests, affect their overall combat readiness, and lead to an increasing amount spent on medical treatment. Recently, the US Army changed their physical fitness test to the Army Combat Fitness Test (ACFT) which is a more full body, functional, and fatiguing test.1 Fatigue of the shoulder and scapular musculature has been reported to lead to alterations in scapular kinematics. Alterations to normal scapular kinematics have been connected to shoulder pain/injuries. 2

Purpose: The purpose of this study was to explore the relationship between scapular dyskinesis and ROTC Cadets scores on three exercises of the ACFT (leg tuck, power throw, and T-pushups). The hypothesis was that ROTC cadets with scapular dyskinesis will score lower on the standing power throw, two minutes T-pushups, and the hanging leg tucks.

Methods: Fourteen Army ROTC cadets (172.6 ± 10 cm, 77.1 ± 11.7 Kg, 5 females, 9 males) participated in the research study. Participants completed patient-reported outcome forms prior to testing. Cadets performed 30 repetitions of weighted shoulder motion in the frontal plane. Shoulder musculature strength measurements were recorded prior to and immediately after the fatigue protocol using a handheld dynamometry. The scapular dyskinesis test was performed prior to and during the last five repetitions of the fatiguing protocol. During the school year the Cadets were then tested on the Army Combat Fitness Test during their PT sessions with ROTC.

Results: Prior to the fatigue protocol two out of fourteen were categorized with scapular dyskinesis on the right and left sides. Following the fatigue protocol seven out of fourteen (p = 0.008) Cadets were categorized with right side scapular dyskinesis and five out of fourteen (p = 0.008) were categorized with left side scapular dyskinesis. Participants graded with scapular dyskinesis on the left side following the fatigue protocol demonstrated lower muscle strength for the external rotation (p = 0.029), internal rotation (p = 0.026), abduction (p = 0.021), serratus anterior (p = 0.37), lower trapezius (p = 0.24), and middle trapezius (p = 0.028). No significant strength differences were found on the right side. The ACFT scores in the total of three upper extremity components (standing power throw, T-pushups, and hanging leg tucks) while not statistically significant were lower in the participants with scapular dyskinesis (right = 190.60 ± 36.3; left = 182.50 ± 36.4) than in those with normal scapular kinematics (right = 237.33 ± 61.4; left = 235.29 ± 56.4).

Conclusions and Practical Relevance: Repeated shoulder motion caused an increase in the amount of scapular dyskinesis in Army ROTC Cadets. Those who produced scapular dyskinesis in a fatigued state tended to show lower scores on the upper extremity components of the ACFT than those who did not produce scapular dyskinesis. The results may suggest a link between scapular dyskinesis, strength of the shoulder and scapular muscles, and upper extremity function. Improving the strength of the musculature might decrease the fatiguing effects of repeated shoulder motion leading to overall improvement in upper extremity function, in turn resulting in better performance outcomes.

Subject(s)

Kinematics.

Dynamics, Rigid.

Shoulder joint -- Physiology.

Shoulder pain -- Treatment.

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