The effects of fatigue on scapulothoracic kinematics during total shoulder abduction.

Bang, Erik Hofman ; Kvist, Martin

4. semester

Sports Science, Master

2016

2016-12-06

39 pages

Introduction: Recently, scapular muscle fatigue during an elevation task was found to alter scapular kinematics. Muscle fatigue may be a key factor in the development of shoulder and neck discomfort and pain. Shoulder girdle muscle fatigue has been shown to alter scapulothoracic kinematics. However it is unclear whether muscle fatigue results in increased or decreased scapular upwards rotation. Aim: The focus of this study is to examine the effects of shoulder muscle fatigue on the 3-dimensional scapular kinematics during arm elevation, using the Qualisys motion capture system. We aim to examine whether an upwards displacement of the humerus, increased anterior tilting of the scapula and ncreased upwards rotation will result from fatigue, kinematic changes suspected to cause a shortening of the subacromial space and leading to the development of shoulder pain. Methods: Nine healthy subjects took part in the study and data for six subjects completing five repetitions of elevation and lowering in the scapular plane abduction was obtained, before and after a fatigue protocol. Maximum voluntary sometric contraction force which served as a measure of local muscle fatigue in this study was measured with the subjects standing on a force plate performing maximum voluntary isometric contractions of the shoulder while pushing up against a strap attached to the floor besides the force platform. Realtime 3-dimensional kinematics was recorded during the repetitons of shoulder elevation using a Qualisys Motion capture system. Results: There was a significant drop in force between conditions indicating local muscle fatigue. The results of this study indicate that overall muscular fatigue of the shoulder affects scapulothoracic and glenohumeral kinematics. There was a significant effect of fatigue for Anterior/posterior tilt of the scapula after the fatiguing exercise, with a mean increase of 4.13°and a maximal increase of 7.73°anterior tilt however small, this represented a change in rotation of almost 45%. Conclusion: This study showed that small but potentially clinically significant changes in scapular kinematics were found after a shoulder fatigue protocol. An increase in scapular anterior tilt, humeral internal rotation, flexion and abduction in the early phases of shoulder elevation was found after fatigue

Shoulder Pain ; Kinematics ; Overhead athlete ; Scapula

Download
View record in AAU Student Projects