Comparison of electromyographic activity of the lower trapezius and serratus anterior muscle in different arm-lifting scapular posterior tilt exercises.
Scapular posterior tilt (SPT) is important in arm elevation. It occurs mainly toward the end of range, allowing the rotator cuff to clear the anterior acromion. The muscles involved in SPT are serratus anterior (SA) and lower trapezius (LT). This study investigated muscle activity in 4 SPT strengthening exercises during arm elevation above 90°, in a younger, healthy population.
This EMG study investigated the following exercises, which involved lifting the arm, while positioned above the head:
1. Wall-facing arm lift
2. Prone arm lift
3. Backwards rocking (while kneeling) arm lift
4. Backwards rocking diagonal arm lift (the arm is abducted to about 120°)
The results were that LT activity was significantly higher during backwards rocking diagonal arm lift, while SA activity was significantly higher during the backwards-rocking arm lift. It may be that these are the exercises that might produce the most benefit where shoulder impingement is causing pain above 90°.
It would have been interesting to have measured the SPT, to see if it correlated with increased LT or SA activity. The next study we would like to see would involve the effects of a strengthening programme, using these exercises, on a population with subacromial impingement > From Ha et al., Phys Ther Sport 13 (2012) 227-232. All rights reserved to Elsvier Ltd.
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(Image by: Phillip Hughes)