Electromyographic Analysis of the Rotator Cuff and Deltoid Musculature During Common Shoulder External Rotation Exercises

Michael M. Reinold, DPT, ATC1
Kevin E. Wilk, PT2
Glenn S. Fleisig, PhD3
Nigel Zheng, PhD4
Steven W. Barrentine, MS5
Terri Chmielewski, PT, PhD6
Rayden C. Cody, MD7
Gene G. Jameson, MA5
James R. Andrews, MD8

J Orthop Sports Phys Ther 2004;34:385-394.H

Study Design: Prospective single-group repeated-measures design.
Objectives: 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 and Measures: EMG measured using intramuscular electrodes were analyzed in 10 healthy subjects during 7 shoulder exercises: prone horizontal abduction at 100° of abduction and full external rotation (ER), prone ER at 90° of abduction, standing ER at 90° of abduction, standing ER in the scapular plane (45° abduction, 30° horizontal adduction), standing ER at 0° of abduction, standing ER at 0° of abduction with a towel roll, and side lying ER at 0° 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