Electromyographic activity in the immobilized shoulder girdle musculature during scapulothoracic exercises.
OBJECTIVE
To quantify the electromyographic activity in the shoulder girdle musculature during scapulothoracic exercises performed in a shoulder immobilizer in asymptomatic men.


METHODS
Descriptive.


METHODS
Motion analysis laboratory at a tertiary care center.


METHODS
Five asymptomatic male volunteers ages 24 to 32 years.


METHODS
Fine-wire (supraspinatus, infraspinatus, upper subscapularis) and surface (deltoids, trapezii, biceps, serratus anterior) electrodes recorded electromyographic activity from each muscle during scapular clock, elevation, depression, protraction, and retraction exercises completed during a single testing session in random order.


METHODS
Mean peak normalized (percentage of maximal voluntary contraction [MVC]) electromyographic activity of each muscle during each exercise.


RESULTS
Biceps activity was uniformly low (<20% MVC), whereas upper subscapularis activity was uniformly high (40%-63% MVC). Both scapular depression and protraction elicited low activity (<20% MVC) in the supraspinatus, infraspinatus, anterior deltoid, and biceps brachii muscles, while generally producing greater than 20% MVC activity in the trapezii and serratus. Scapular depression produced the largest serratus anterior activity (47% MVC).


CONCLUSIONS
These data are the first to describe the electromyographic activity during scapulothoracic exercises while in a shoulder immobilizer. Based on electrophysiologic data in normal volunteers, our findings suggest that during periods of shoulder immobilization: (1) scapular depression and protraction exercises could potentially be safely performed after rotator cuff repair to facilitate scapulothoracic rehabilitation, (2) all exercises studied could potentially be safe after superior labral anteroposterior shoulder repair, and (3) all exercises studied should be avoided after subscapularis repair. Further investigation in symptomatic individuals may facilitate refinement of these recommendations.
Smith
Jay
J
Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, MN 55905, USA. smith.jay@mayo.edu
Dahm
Diane L
DL
Kaufman
Kenton R
KR
Boon
Andrea J
AJ
Laskowski
Edward R
ER
Kotajarvi
Brian R
BR
Jacofsky
David J
DJ
D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005081:Exercise Therapy / Q000379:methods*; D006801:Humans; D007103:Immobilization; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012785:Shoulder Joint / Q000502:physiology*