Unsung Hero of the Musculoskeletal System: Serratus Anterior

December 16, 2015 7:24 pm Published by Leave your thoughts

 

by Joe Giandonato, MBA, MS, CSCS

Manager of Health Promotion

Drexel University

Last year, I authored a piece which underscored the importance of not neglecting the gluteus medius, a

muscle that I consider to be the epoxy which cohesively stabilizes the hip girdle and femurs.

Those who want to squat big weights and pull five plus plates would take heed to the advice of

incorporating concerted gluteus medius training within their program as it staves off a volley of

compensatory strategies which shift the stress to the muscles of the lower back and those crossing the

knees.

On the slow twitch side of the continuum, runners rely on the gluteus medius to lock down stability in

the frontal plane through continued abduction torque on the stance, or rear leg, keeping the hips even

during gait. A breakdown in gait, such as the hips dropping as seen during Trendlenburg sign, stretches

the IT band across the femur and yanks on the lateral epicondyle of the knee and adjacent patella which

over time can elicit knee pain — just one of the many ailments caused by a dormant gluteus medius or

one that is comparatively weaker to its secondary and tertiary counterparts in hip abduction and

internal rotation.

This year, however, I present to you a long overdue overview of a muscle of the upper body, which

wields comparable reverence — the serratus anterior.

The serratus anterior, or SA for short, comprises a scapular force couple with the upper and lower

trapezius muscles which facilitates upward rotation of the scapula — a movement which is conducive to

multiple activities of sport, daily living, and hoisting heavy ass iron overhead.

Innervated by the long thoracic nerve and emanating from the external sufrace of the lateral aspects

from the first to ninth ribs, the serratus anterior, which fleshes into the entire medial border to the

scapulae, with increased pennation near the inferior aspect of the scapulae, also protracts the shoulder.

Protraction is bad, right? Well that’s what the loosely credentialed pseudo-physical therapist who’s

never benched more than 95 pounds would lead you to believe.

In activities of daily living, protraction is key, such as reaching for that vase wobbling on the edge of the

kitchen counter. In sports, imagine diving out of bounds to save a loose ball on the basketball court or

diving over the goal line for a touchdown with the arms outstretched (and protracted) so the ball clears

the end zone’s plane.

The serratus anterior actually powers pushing exercises as it stabilizes and slides the scapulae forward

and emits force which is transmitted through the glenohumeral joint.

Activities involving horizontal pushing become labored among persons with exhibiting inhibited function

of the serratus anterior. Foo and Swann (1983) noted that an impinged or damaged long thoracic nerve

which feeds the serratus anterior, contributing to partial paralysis manifested as scapular winging and

subsequent abnormal upward and downward rotation or leading to full paralysis thusly degrading the

structures enveloping the shoulder girdle and craniocervical regions.

Neumann (2002) highlighted an action of the serratus which delineates it from the other “pushing

muscles” such as the pectoralis and triceps as the bilateral protraction provided by the serratus elevates

the thorax in the direction of the fixed scapulae, which is evidenced in the push up plus.

Alternative closed chain variations which train protraction, include the Serratus Slide and progress to

more difficult variations, which involve a greater degree of scapular stability under load of bodyweight,

including the:

The Prone Serratus Press Up may be appropriate for individuals with lesser relative strength. Just be

sure to control retraction and protraction and maintain a neutral neck throughout the movement.

Open chain exercises may be warranted for those who are beginning to integrate activities of sport, such

as the Serratus Punch and the Dynamic Hug, which when performed with an upwardly rotated scapulae,

elicited beyond 20% greater EMG activity than a few of its above mentioned counterparts (Decker et al,

1999). The hug exercise alternatively be performed on a cable stack as depicted in the video, which is an

appropriate regression for those who cannot adroitly perform upward rotation with protraction as the

height of the handles can be predetermined.

These movements can be incorporated prior to or following traditional strength training exercises. In my

experience, a greater emphasis should be placed on harnessing tension to establish relative stiffness of

the scapulae rather than powering through the repetitions. I have found that committing the latter

rouses the upper trapezius and deltoids — two groups that usually do not need to be activated in those

involved in laborious occupations and strength sports.

Brian Rugghia contributed to this article.

References

Foo, C.L. & Swann, M. (1983). Isolated paralysis of the serratus anterior. The Journal of Bone and Joint

Surgery, 65, 552-556.

Neumman, D.A. (2002). Kinesiology of the Musculoskeletal System. St. Louis, MO: Mosby.

Decker, M.J., Hintermeister, R.A., Faber, K.J., & Hawkins, R.J. (1999). Serratus anterior muscle activity

during selected rehabilitation exercises. The American Journal of Sports Medicine, 27, 784-791.

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