Electromyographic analysis of the rotator cuff and deltoid musculature during common shoulder external rotation exercises.
METHODS
Prospective single-group repeated-measures design.


OBJECTIVE
To quantify electromyographic (EMG) muscle activity of the infraspinatus, teres minor, supraspinatus, posterior deltoid, and middle deltoid during exercises commonly used to strengthen the shoulder external rotators.


BACKGROUND
Exercises to strengthen the external rotators are commonly prescribed in rehabilitation, but the amount of EMG activity of the infraspinatus, teres minor, supraspinatus, and deltoid during these exercises has not been thoroughly studied to determine which exercises would be most effective to achieve strength gains.


METHODS
EMG measured using intramuscular electrodes were analyzed in 10 healthy subjects during 7 shoulder exercises: prone horizontal abduction at 100 degrees of abduction and full external rotation (ER), prone ER at 90 degrees of abduction, standing ER at 90 degrees of abduction, standing ER in the scapular plane (45 degrees abduction, 30 degrees horizontal adduction), standing ER at 0 degrees of abduction, standing ER at 0 degrees of abduction with a towel roll, and sidelying ER at 0 degrees of abduction. The peak percentage of maximal voluntary isometric contraction (MVIC) for each muscle was compared among exercises using a 1-way repeated-measures analysis of variance (P<.05).


RESULTS
EMG activity varied significantly among the 7 exercises. Sidelying ER produced the greatest amount of EMG activity for the infraspinatus (62% MVIC) and teres minor (67% MVIC). The greatest amount of activity of the supraspinatus (82% MVIC), middle deltoid (87% MVIC), and posterior deltoid (88% MVIC) was observed during prone horizontal abduction at 100 degrees with full ER.


CONCLUSIONS
Results from this study provide initial information to develop rehabilitation programs. It also provides information helpful for the design and conduct of future studies.
Healthsouth Rehabilitation, American Sports Medicine Institute, Birmingham, AL 35205, USA. michael.reinold@healthsouth.com
Michael M
MM
Reinold
Kevin E
KE
Wilk
Glenn S
GS
Fleisig
Nigel
N
Zheng
Steven W
SW
Barrentine
Terri
T
Chmielewski
Rayden C
RC
Cody
Gene G
GG
Jameson
James R
JR
Andrews
D000328:Adult; D004576:Electromyography; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology; D011446:Prospective Studies; D012399:Rotation; D017006:Rotator Cuff / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology