Surface electromygraphic analysis of the lower trapezius muscle during exercises performed below ninety degrees of shoulder elevation in healthy subjects.

BACKGROUND

The lower trapezius is an important muscle for normal arthrokinematics of the scapula. In the early stages of rehabilitation, it is generally accepted to perform exercises with the shoulder kept below 90° of elevation in order to minimize risk for shoulder impingement. Few exercises for the lower trapezius have been studied which maintain the shoulder below 90° of humeral elevation.

OBJECTIVE

To identify therapeutic exercises performed below 90° of humeral elevation that activate marked levels of lower trapezius electromyographic (EMG) activity.

METHODS

SURFACE EMG ACTIVITY OF THE LOWER, MIDDLE, UPPER TRAPEZIUS, AND SERRATUS ANTERIOR WAS COLLECTED BILATERALLY ON FIFTEEN HEALTHY SUBJECTS DURING FOUR EXERCISES: the press-up, unilateral scapular retraction with the shoulder positioned at 80° of shoulder flexion, bilateral shoulder external rotation, and unilateral scapular depression.

RESULTS

The press-up exercise elicited marked lower trapezius EMG activity, moderate upper trapezius EMG activity, and a high ratio of lower trapezius to upper trapezius EMG activity. Scapular retraction produced marked EMG activity of both the lower and upper trapezius and moderate activity of the middle trapezius. Bilateral shoulder external rotation generated moderate lower trapezius EMG activity, minimal upper trapezius activity, and the highest ratio of lower trapezius to upper trapezius EMG activity. Scapular depression produced moderate lower trapezius EMG activity, mimimal upper trapezius EMG activity, and a moderately high ratio of lower trapezius to upper trapezius EMG activity.

DISCUSSION AND CONCLUSIONS

This study identified two exercises performed below 90° of humeral elevation that markedly activated the lower trapezius: the press-up and scapular retraction.