Date of Award


Degree Name

Athletic Training


College of Health Professions

Type of Degree


Document Type


First Advisor

Mark Timmons

Second Advisor

Gary McIlvain

Third Advisor

Joseph Beckett

Fourth Advisor

John Jasko


Introduction: The medial elbow is supported from valgus loading with the ulnar collateral ligament (UCL), the flexor pronator mass (FPM), and the radial head. Fatigue of muscle can lead to a decrease in force production. The decrease in force production can lead to a decrease in joint stability. This study tested the effect of fatigue of the FPM muscles on the width of the medial joint space.

Methods: Thirty-one participants volunteered for this study (18 female and 12 male, 1 excluded; mean height 170.2±10.1 cm, mean weight 71.2±15.6 kg, mean age 21.53±1.87 years old). Ultrasound images of the width of the medial joint space of the non-dominant left elbow of right handed participants were collected while unstressed and during valgus loading; images were collected prior to and immediately following a wrist flexor exercise fatigue protocol. The fatigue protocol consisted of three sets of thirty wrist flexion repetitions using a blue Theraband™. Paired t-tests were conducted to assess muscle fatigue within wrist flexion and extension, grip strength, and participants’ perceived exertion. A two way repeated measures design, stress by fatigue was used to assess the effect of FPM fatigue on medial elbow width during valgus loading.

Results:The wrist flexion strength measured decreased (7.5%) from an average of 22.6±7.7 lbs. to 20.9±8.3 lbs. after the fatigue protocol (t=3.840; p=0.001). Increases in perceived exertion after each set of thirty repetitions was not statistically significant (t=1.928; p=0.064). The medial elbow width increased between unstressed (2.8±0.1 mm) and stressed (3.6±0.1 mm) conditions (p

Discussion: The fatigue protocol achieved FPM fatigue, evidenced by the 7.5% decrease in the wrist flexor strength. Following the fatigue protocol there was a greater increase in the width of the medial joint space with the applied valgus stress. This research establishes the significance of FPM fatigue on width of the medial joint space under valgus loads. Further research should be conducted to identify the effect of FPM fatigue following throwing.



Sports sciences.