Scapulothoracic Muscles and Pain

As I mentioned in Part 1, weakness or poor neuromuscular control of the periscapular muscles has been implicated in subacromial impingement1,2, lateral epicondylalgia3-5, cervicogenic headache6, and neck pain7,8.

Specifically, insidious onset of neck pain and whiplash associated disorder (WAD) have been linked with a significant delay in and shorter duration of serratus anterior activity bilaterally during arm elevation9. A similar study found decreased serrates anterior activation in individuals with acromioclavicular osteoarthritis and rotator cuff disease.10

Although a cause-and-effect relationship cannot be confirmed, this preliminary evidence still lends support for targeting the periscapular muscles in individuals with neck or shoulder pain.

EMG Activity and Exercise Goals

According to Reiman et al.11 and Escamilla et al.12, moderate EMG activation (21-40% MVIC) is best used to facilitate endurance and neuromuscular re-education; high activation (41-60+% MVIC) – to promote strength gains.

From Biomechanics to Exercises

Serratus Anterior

Primary Function: scapular upward rotation, external rotation, posterior tilt at the acromioclavicular joint, protraction of the clavicle at the sternoclavicular joint.

Origin: External surfaces of lateral aspect of 1st-8th ribs

Insertion: Anterior surface of medial border of scapula

The SA is often activated with scapular protraction. The exercises yielding the highest MVIC for the serratus anterior include:

  • dynamic hug13
  • push-up plus13
  • scaption with external rotation14
  • diagonal PNF (shoulder flexion, horizontal flexion, external rotation)15
  • shoulder abduction in scapular plane above 120 degrees15

The upper trapezius (UT) often compensates for a weak or inhibited serratus anterior, so it’s beneficial to selectively activate the SA in lieu of the UT. According to Cools and colleagues, the best SA:UT ratio is achieved in:

  • high row
  • forward shoulder flexion
  • scaption with external rotation14
Serratus Anterior
Prone Push Up with Plus
Serratus Anterior
Dynamic Hug with Resistance
[Table] MVIC values for SA exercises

Levator Scapulae

Primary Functions: scapular elevation, glenoid cavity inferior tilt through upward scapular rotation

Origin: Posterior tubercles of transverse processes of C1-C4 vertebrae

Insertion: Medial border of scapula superior to root of scapular spine

These muscles have received little attention in the literature compared the SA or trapezius. In a study, Moseley and colleagues discovered that the levator scapulae achieves the highest activity in:

  • rowing
  • horizontal abduction
  • shrug
  • horizontal abduction with ER
  • prone shoulder extension16
[Table] MVIC values for Levator Scapulae exercises

Rhomboids

Primary Functions: Retraction of the scapula; upward rotation to depress glenoid cavity; scapular attachment to thoracic wall

Origin: nuchal ligament; spinous processes of C7, T1 and T2-T5 vertebrae

Insertion: smooth triangular area at medial end of scapular spine; medial border of scapula from level of spine to inferior angle

The rhomboids achieve the highest MVIC during:

  • ER at 90° of abduction17
  • ER at 0° of abduction17
  • horizontal abduction16
  • shoulder extension17
  • scaption16
Levator Scapulae
Prone Shoulder Row
Rhomboid
Shoulder External Rotation at 90° Abduction with Dumbbell
[Table] MVIC values for rhomboid muscle exercises

Choosing the Best Exercise

These studies give us a glimpse into properly selecting exercises, yet very few exercises have been or will ever be studied.

When choosing an exercise for your patient, be sure to consider:

  • the biomechanics of the movement,
  • current evidence for or against the exercise,
  • your patient’s presentation, and goals for treatment.
  • aggravating movement(s) or comparable signs

About the Author John Snyder, PT, DPT, OCS, CSCS

I am a Physical Therapist, a Board Certified Orthopaedic Specialist, a Strength & Conditioning Specialist, an Educator, and a Research Junkie. My goal is to provide resources for orthopedic and sports medicine clinicians to keep up to date with the current literature and allow them to translate it to their practice.

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