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Tuesday, June 6, 2023

Scapular Muscle Performance and Lateral Epicondylagia

Brent Brookbush

Brent Brookbush


Research Review: Scapular Muscle Performance and Lateral Epicondylagia

By Jinny McGivern, DPT, PT, Certified Yoga Instructor

Edited by Brent Brookbush DPT, PT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Day, J. M., Bush, H., Nitz, A. J., & Uhl, T. L. (2015). Scapular Muscle Performance in Individuals With Lateral Epicondylalgia. Journal of Orthopaedic & Sports Physical Therapy, (Early Access), 1-35. ABSTRACT

Dr. Brookbush instructs Krystal Salvent on performing a therapeutic exercise for forearm dysfunction called a "Reverse Tyler Twist"
Caption: Dr. Brookbush instructs Krystal Salvent on performing a therapeutic exercise for forearm dysfunction called a "Reverse Tyler Twist"

Tyler Twist performed by Krystal Salvent with instruction from Dr. Brookbush (c) Brookbush Institute

Why is this relevant?: Lateral elbow pain is a condition which affects individuals in both the athletic and general populations. It frequently has high rates of recurrence and impacts an individual's ability to perform regular daily tasks such as lifting, carrying and pulling. The relationship between the scapula and the glenohumeral joint has been well established and extensively researched. This article provides evidence of a relationship between scapular stability and more distal segments of the upper extremity. It may indicate that assessment of scapular kinematics and scapular strength, as well as interventions to improve scapular kinematics may be appropriate for individuals with lateral elbow pain.

Study Summary

Study Design Descriptive, laboratory based, cross sectional study
Level of Evidence VI - Evidence from a single descriptive study
Subject Demographics

28 individuals with Lateral Epicondylagia (LE) were recruited from outpatient PT clinics - (LE group). 28 age and sex matched controls were recruited from the community - (CON group).

  • Age: 46.8 +/- 8.8 yrs (LE group); 46.1 +/- 9.2 yrs (CON group).
  • Gender:15 women/13 men in LE group; 15 women/13 men in CON group
  • Characteristics: Individuals with and without lateral epicondylagia
  • Inclusion Criteria: LE group - individual seeking PT treatment for unilateral elbow pain,  age 18-65, reproduction of elbow pain (positive test) from two of following tests for lateral epicondylagia -  palpation of lateral epicondyle and wrist extensor mass; Mill's test (passive stretching of wrist extensors); Strength assessment of grip with handheld dynamometer; Cozen's test (manually resisted wrist extension); Maudsley's test (manually resisted middle digit extension).
  • Exclusion Criteria: Both groups - Peripheral neuropathy due to diabetes; progressive neurological disorder; cancer; infection in the spine or upper extremity; upper motor neuron lesion (CVA, TBI, etc); Fibromyalgia; surgery on the upper quadrant within the previous 6 months; score of less than 10% on shortened version of the Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH).  CON group - any upper quarter musculoskeletal complaints or upper quarter or trunk surgeries over the past 6 months; positive test for lateral epicondylagia (as listed above); QuickDASH score greater than 10% (score of 0-10% observed to be within normal limits for general population).
Outcome MeasuresDescriptive Data
  • Mechanism of Injury - LE group
  • Duration of Symptoms - LE group
  • QuickDASH scores - Both groups

For the 3 variables below, two sets of comparisons were performed:

  • The involved limb of subjects in LE group and the matched (based on limb dominance) limb of those in CON group.
  • The involved limb of subjects in LE group was and the  contralateral limb

1) Scapular Muscle Strength

Maximal Voluntary Contraction for the following muscles (3 trials measured via handheld dynamometry and averaged):

2) Scapular Muscle Endurance

Time individual could maintain UE position. (Individuals were positioned in prone, set up with a cuff containing weight equal to 1% of body weight and instructed to hold tested arm in 135 degrees abduction parallel to trunk - position standardized with ruler for level).

3) Scapular Muscle Thickness (measured via Ultrasound in sitting at rest and during arm lift task in the scapular plane with cuff weight equivalent to albs)

ResultsDescriptive Data

  • QuickDASH scores (p<.001)
  • LE group: 40.6 +/- 16.3
  • CON group: 2.6 +/- 3.5

Body Mass

  • LE group: 83.8 +/- 15.9
  • CON group: 73.3 +/- 13.3

Mechanism of Injury for LE group

  • Insidious Onset: 79%
  • Traumatic Event: 21%
  • Median duration of symptoms: 12 weeks
  • 53% of LE group reported dominant side as involved side.
  • No significant differences between groups for age, height or shoulder activity.


1) Scapular Muscle Strength

  • MT: CON group demonstrated significantly greater strength than LE group (p=.031)
  • There was no significant difference in strength between involved and un-involved limbs in LE group (p=.26).
  • LT: CON demonstrated significantly greater strength than LE group (p=.006).
  • The involved limb demonstrated significantly reduced strength as compared to un-involved (p=.023).
  • SA: CON group demonstrated significantly greater strength than LE group (p<.001).
  • The involved limb demonstrated significantly reduced strength as compared to the uninvolved (p=.016).

* While statistically significant, differences between involved and un-involved limb for LT and SA strength did not exceed the measurement error value for using a handheld dynamometer.

2) Scapular Muscle Endurance

  • CON group demonstrated significantly greater endurance over LE group (p = .003).
  • There was no significant difference between involved and uninvolved limbs of subjects with LE (p=.096).

3) Muscle Thickness

  • Both groups demonstrated a significant change in thickness between rest & contracted state for the SA & LT.  There was no significant difference in thickness in either state or change in thickness between groups.
  • There was no significant difference in muscle thickness between involved and uninvolved limbs for the resting or contracted states or the change in thickness between states.
ConclusionsThis research demonstrates the connection of the more proximal and distal segments of the upper extremity.  The elbow joint and the scapula thoracic joint demonstrate a relationship in spite of the fact that there is no single muscle that crosses both joints.
Conclusions of the Researchers

Individuals with lateral epicondylagia demonstrate significantly reduced strength of the LT and SA, as well as reduced endurance of scapula stabilizing muscles when compared to non painful controls.  This difference was not significant between involved and uninvolved limbs within the same subject.  Clinicians should consider assessment and treatment of scapular stabilizing muscles when an individual presents with signs and symptoms of lateral epicondylagia.

Self-administered Extensor Release with a Flexbar

Review & Commentary:

This research had many strong points to its methodology and design. The experimental and control groups were matched by age and sex. The researchers utilized clear diagnostic criteria to establish the diagnosis of lateral epicondylagia, thus providing the reader with a clear picture of the clinical presentation of the symptomatic individuals. The pain free controls were screened to ensure that they did not have any positive tests associated with lateral epicondylagia. One of the strongest methodological choices the authors made was to perform comparisons to both an asymptomatic side, as well as to pain free controls. Clinically we often compare the affected side to the unaffected side during evaluation. This research reminds us to consider that the asymptomatic side may also be dysfunctional, therefore may not serve as an ideal standard for goal setting. Future research may want to consider comparisons between symptomatic and asymptomatic sides, symptomatic side and healthy controls, and between the asymptomatic side and a healthy control to allow better understanding of how the opposite side of the body is affected when a unilateral injury occurs. In terms of data collection, randomization procedures were used for the order of measurements taken of scapular muscle strength and for order of dominant vs. non-dominant limb. A calibrated handheld dynamometer was used for strength measures, thus providing objective, quantifiable data. Muscle thickness was measured using established methods for ultrasound imaging. Appropriate procedures were used to ensure standardization of patient position across all subjects and measures.

This research had many strengths, however also has its limitations. It would have been favorable if the sample size could have been larger than 28. Muscle thickness outcome data was only collected from 18 individuals. Future research should include a larger sample size for all data points. The researcher who performed the scapula muscle strength assessment was not blinded to the subject's group assignment or involved limb, thus an investigator bias could potentially have been introduced. It is important to note that the scapular muscle endurance outcome was measured via an isometric hold. Muscle performance may differ if the endurance task selected required movement through a range of motion. Different upper extremity motions were selected for the strength, and endurance and muscle thickness testing, therefore it is not possible to get a complete picture of the various components of muscle function for a specific movement. For example, the serratus anterior strength test was performed for protraction in supine, however the change in muscle thickness was assessed in sitting via abduction in the scapular plane. Future research should examine how different muscle strength, endurance and change in thickness are correlated across specific tasks. Because scapula stability has been assessed, it may be interesting for future researchers to examine how stability of the cervical spine relates to incidences of lateral elbow pain. The cervical spine and scapula are intimately connected via several muscles as well as neuromuscular tissue as it makes its journey from the trunk to the upper extremity. Finally, the authors note that because of the design of the study it is not possible to determine if scapular muscle weakness is a pre-disposing factor to lateral elbow pain, or a result of it due to a pain related centrally mediated pattern of inhibition of proximal musculature.

The authors hypothesize that an impaired ability to stabilize the scapula places greater demands on the distal segments of the upper extremity during functional activities. As stated above, based on the design of this study it is not possible to know which came first. It is possible that impaired scapula stability can contribute to an initial injury of lateral epicondylagia. It is also possible that lateral elbow pain may precede the development of scapula muscle weakness, but that impaired scapula stability may contribute to the chronicity of the condition and may set the stage for other upper extremity injuries.

An interesting finding in this study deserves further investigation. Despite marked changes in muscular endurance, there was no change in thickness of the affected musculature. This may imply that neuromuscular reflex (inhibition), altered length/tension relationships, or increased workload caused by soft tissue restriction may be the cause of decreases in endurance and force output in those exhibiting dysfunction, rather than atrophy as result of disuse or deconditioning.

Why is this study important?

This study is important because it highlights what may be a previously overlooked relationship between the scapula and more distal segments of the upper extremity. It encourages the human movement professional to develop a comprehensive strategy which includes the trunk, scapula and all distal segments of the upper extremity to correct postural and movement dysfunction in order to reduce pain and enhance performance. It is essential to address more than just the segment that is the location of pain.

How does it affect practice?

While we cannot say definitively that scapular muscle weakness results in lateral elbow pain, research has demonstrated that dysfunctional scapula stabilization is correlated with pain in other joints and tissues of the body including but not limited to the shoulder , thoracic spine cervical spine , and even in those with distal radius fractures . Therefore scapula stabilization activities, including endurance activities, should always be included in any program designed to address the upper extremity. Many of the symptomatic individuals in the sample of the study described an insidious onset of lateral elbow pain, implicating a possible mechanism of "repetitive stress". It is possible that strain accumulates at an accelerated pace in distal structures (such as the wrist extensors) once scapula musculature has fatigued and is unable to efficiently stabilize. More research is needed to fully examine this topic; however, the human movement professional may integrate the information proposed in this study and carefully record and evaluate outcomes.

How does it relate to Brookbush Institute Content?

This research supports the Brookbush Institute's predictive model of postural dysfunction for the Upper Body (UBD) . The serratus anterior and lower trapezius are two muscles that this model considers to have a propensity toward being long and under-active. When designing a program to enhance scapular stability, it is important to make it possible for the scapula to achieve a more optimal position on the rib-cage. This is achieved by reducing the excess activity and increasing the length of short/overactive muscles using release and stretching  techniques (i.e. pectoralis minor , levator scapula and rhomboids ) and addressing hypomobility of affected joints using mobilization techniques (i.e. thoracic spine , glenohumeral joint and elbow ). This sets the stage for more optimal length/tension relationships, neuromuscular activity and arthrokinematics. These techniques would be followed by activation techniques for the serratus anterior and lower trapezius . Because of the high frequency of lateral epicondylagia in athletic populations, it is essential to progress to "reactive activation" techniques that challenge these muscles to perform a time dependent task (i.e. a catch or a throw). The videos below describe the anatomy of scapula muscles, isolated activation and reactive activation techniques for the serratus anterior  and lower trapezius and a taping technique to help facilitate increased activity of the lower trapezius over a longer period of time.

Scapular Muscles

Trapezius Isolated Activation

Serratus Anterior Isolated Activation

Serratus Anterior Activation Progressions

Trapezius Reactive Activation

Serratus Anterior Reactive Activation

Lower Trapezius Activation Taping

© 2015 Brent Brookbush

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