Scapulothoracic and glenohumeral kinematics following an external rotation fatigue protocol.
METHODS
Repeated-measures experimental design.


OBJECTIVE
To determine the effects of shoulder external rotator muscle fatigue on 3-dimensional scapulothoracic and glenohumeral kinematics.


BACKGROUND
The external rotator muscles of the shoulder are important for normal shoulder function. Impaired performance of these muscles has been observed in subjects with impingement syndrome and it is possible that external rotator muscle fatigue leads to altered kinematics of the shoulder girdle.


METHODS
Twenty subjects without a history of shoulder pathology participated in this study. Three-dimensional scapulothoracic and glenohumeral kinematics were determined from electromagnetic sensors attached to the scapula, humerus, and thorax. Surface electromyographic (EMG) data were collected from the upper and lower trapezius, serratus anterior, anterior and posterior deltoid, and infraspinatus muscles. Median power frequency (MPF) values were derived from the raw EMG data and were used to indicate the degree of local muscle fatigue. Kinematic and EMG measures were collected prior to and immediately following the performance of a shoulder external rotation fatigue protocol.


RESULTS
After completing the fatigue protocol subjects demonstrated less external rotation of the humerus. Additionally, they had less posterior tilt of the scapula in the beginning phase of arm elevation, and more scapular upward rotation and clavicular retraction in the mid ranges of arm elevation.


CONCLUSIONS
Performance of an external rotation fatigue protocol results in altered scapulothoracic and glenohumeral kinematics. Further studies are needed to investigate the effects of external rotator muscle fatigue on scapulothoracic and glenohumeral kinematics in subjects with shoulder pathology.
Ebaugh
D David
DD
Programs in Rehabilitation Sciences, Drexel University, Philadelphia, PA 19102-1192, USA. debaugh@drexel.edu
McClure
Philip W
PW
Karduna
Andrew R
AR
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002968:Clavicle / Q000502:physiology*; D002985:Clinical Protocols; D004576:Electromyography; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D026741:Physical Therapy Modalities; D017006:Rotator Cuff / Q000503:physiopathology*; D012540:Scapula / Q000502:physiology*; D012785:Shoulder Joint / Q000503:physiopathology*