The purpose of this study was to observe the muscle activity of the muscles surrounding the shoulder (supraspinatus, subscapularis, infraspinatus, trapezius, pectoralis major, anterior deltoid, latissimus dorsi, serratus anterior) during seven shoulder rehabilitation exercises performed with elastic resistance.

Nineteen men with no shoulder abnormalities performed seven core shoulder rehabilitation exercises: external rotation, internal rotation, forward punch, shoulder shrug and seated rowing with a narrow, middle and wide grip using elastic resistance. Each man performed 10 repetitions of each rehabilitation exercise at a pace of 2.5 seconds for each phase.

The researchers observed that the shoulder shrug exercise was the most effective exercise in terms of the number of muscles activated. Creating the highest muscle activity from subscapularis, trapezius and latissimus dorsi muscles. Supraspinatus, infraspinatus, and serratus anterior muscles were also stimulated.

Middle-grip seated rowing exercise was expected to show muscle activity of the trapezius but the only activity observed was in the supraspinatus and subscapularis muscle. Trapezius was activated during wide-grip seated rowing exercise.

The results showed narrow-grip and middle-grip seated rowing exercise create greater peak muscle activity from subscapularis muscle than internal rotation. These results maybe due to the greater position of internal rotation in the narrow-grip and middle-grip seated rowing exercises compared to the wide-grip rowing exercise. Narrow-grip and middle-grip rowing are typically done at the beginning of rehabilitation and these results question its use in early stages of rehabilitation.

Finally, forward punch produced the greatest activity from supraspinatus, serratus anterior and anterior deltoid muscles with additional stimulation of pectoralis major and infraspinatus muscles.

So What?

It is great to see some research showing the benefits of elastic resistance. This gives me more confidence in using them and greater reason to prescribe them to my clients. Especially in the client that is only able to handle low resistance and the goal is muscle activation.

It may not be accurate to assume that since the results above were determined with elastic resistance the same results would be found using free weights or machines. The movements are transferable but the way free weights and machines may affect the muscles activity differently. Plus muscle activity may change with greater resistance.

A key point to remember is each phase of each exercise took 2.5 seconds. It was kept constant with the use of a metronome.
 

For More Details:  Electromyographic Activity and Applied Load During Shoulder Rehabilitation Exercises Using Elastic Resistance Robert A. Hintermeister, PhD, Gregory W. Lange, MS, Jeanne M. Schultheis, Michael J. Bey, MS, and Richard J. Hawkins, MD The American Journal of Sports Medicine, Volume 26, Number 2, 1998.

copyright © Rick Kaselj of Healing Through Movement

Article written by Rick Kaselj - rkaselj@healingthroughmovement.com

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