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Tuesday, June 6, 2023

Muscle Activity of Upper Trapezius and Serratus Anterior Change with Forward Head Posture Correction

Brent Brookbush

Brent Brookbush


Research Review: Muscle Activity of Upper Trapezius and Serratus Anterior Change with Forward Head Posture Correction

By Nicholas Rolnick SPT, MS, CSCS

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

Original Citation:Kwon JW, Son SM, Lee NK. (2015). Changes in upper-extremity muscle activities due to head position in subjects with a forward head posture and rounded shoulders. J Phys Ther Sci. 27: 1739-1742. - ARTICLE

Caption: Forward-Head-Posture-FIX-Discount

Why is this relevant?: Forward head, rounded shoulder posture (FHRSP) is a common postural fault observed in fitness, performance and rehabilitation settings. Prior research has indicated altered muscle activation of individuals with FHRSP in comparison to normal healthy controls when performing an overhead lifting task (1). The current study adds to this developing body of research by investigating performance of a similar overhead task under different sagittal plane alignments of the head in individuals with FHRSP. The aim of the study was to determine if muscle activation of the upper and lower trapezius , sternocleidomastoid, and serratus anterior  would significantly change with a sagittal plane postural correction without any concomitant musculoskeletal intervention.

Note: FHRSP includes at least two components of the predictive of model of postural dysfunction referred to as "Upper Body Dysfunction (UBD) " by the Brookbush Institute. In practice, these two terms could likely be used interchangeably, however, FHRSP more accurately depicts the results of assessment used for this research study.

Study Summary

Study Design Crossover Design (Every subject served as his/her own controls)
Level of Evidence Level II-2: Case-crossover design with non-randomized control
Subject Demographics
      • Age: Not specified
      • Gender: Not specified
      • Characteristics:
        • 40 subjects with Forward Head, Rounded Shoulder Posture (FHRSP). The way the authors quantified FHRSP was described in other papers on similar topics
          • Forward Head Angle (FHA) defined as less than or equal to 54°
            • A line was drawn between the tragus (ear) and a marker on C7, a second line was drawn horizontally through C7.
            • The angle between these two lines was calculated in degrees
              • This described the position of the head with respect to C7 when viewed from the side
              • A smaller angle indicated more forward head with respect to C7

          • Forward Shoulder Angle (FSA) defined as less than or equal to 50°
            • A line was drawn between the lateral shoulder (acromion) and a marker on C7
            • A line was drawn to the horizontal and the angle of this line between the two points was calculated in degrees
              • This described the position of the shoulder with respect to C7 when viewed from the side
              • A smaller angle indicates more forward shoulders with respect to C7

        • Protocol
          • Each subject was asked to adopt three head positions while in seated posture
            • Natural head position (NHP)
              • Subjects asked to "sit as you usually do" while looking at a fixed point ahead

            • Ideal head position (IHP)
              • Subjects asked to sit with the head in a "balanced" position, which the subjects considered ideal posture without any manual or verbal feedback

            • Corrected head position (CHP)
              • Subjects were placed in a neutral posture by experienced therapists using manual and verbal feedback

          • Each posture was held for 10 seconds x 3 sets with a 10-second rest period between repetitions
          • Head and shoulder postures were assessed using digital image technology to capture sagittal plane alignment of the upper body in the seated position
            • Markers were placed on the right tragus (ear), acromion, and C7 spinous process.

          • Muscle activity was measured using four-surface electromyography
            • Sternocleidomastoid (SCM) electrode was placed on a lower third of the line connecting the sternal notch and the mastoid process
            • Upper trapezius (UT) electrode was placed lateral to the midpoint of an imaginary line formed by the posterior aspect of the acromion and the C7 spinous process
            • Lower trapezius (LT) electrode was placed next to the medial edge of the scapula at an oblique angle of 55°
            • Serratus anterior (SA) electrode was placed on the midaxillary line of the right fifth rib

          • Maximum voluntary isometric contraction (MVIC) was calculated by a 5-second contraction for each muscle (not specified in protocol) using the middle three seconds and discarding the first and last second of contraction
            • Procedure repeated 3 times with a 60-second rest period in-between each trial

          • Experiment consisted of a 180° overhead shoulder elevation task of the right arm in each of the 3 different head positions (NHP, IHP, CHP)
            • Each position was tested for 3 repetitions with a 30-second rest period in-between using 3% body-weight at a self-selected speed with the elbows straight and shoulders non-elevated

        • Statistical Analyses
          • Root mean square values of EMG data were calculated for each condition and mean %MVIC and standard deviations (SD) were reported
          • Demographic data including age, height, and weight were analyzed by One-Way ANOVA (not reported in the paper)
          • Postural angles and muscle activities in each of the muscles during each of the experimental conditions were examined using One-Way ANOVA and Tukey's LSD Post-Hoc Test with a significance level of < 0.05 set for p

    • Inclusion Criteria:
      • Rounded Shoulder, Forward Head Posture

    • Exclusion Criteria:
      • No history of neck or shoulder pain or current pain, upper-limb injury, cervical or thoracic musculoskeletal pathology, or neurological disorders

Outcome Measures FHA, FSA, and Muscle Activities (%MVIC) with Respect to Each Postural Condition (NHP, IHP, CHP) 
FHA° (a,b)49.2 +/- 2.854.5 +/- 3.159.6 +/- 3.1
FSA° (a,b)49.2 +/- 5.256.4 +/- 7.360.6 +/- 7.1
SCM4.1 +/- 2.54.5 +/- 2.95.6 +/- 3.7
UT (a,b)39.8 +/- 10.133.1 +/- 9.627.7 +/- 6.2
LT25.6 +/- 22.520.1 +/- 15.018.3 +/- 11.7
SA (a,b)59.6 +/- 19.445.3 +/- 14.839.4 +/- 15.7

Figure 1. Data presented as mean +/- SD. (a) is the presence of significant (p < 0.05) changes in EMG activation between NHP and IHP. (b) is the presence of significant (p < 0.05) changes in EMG activation between NHP and CHP.

  • No significant differences among the three head group position groups with respect to age, sex, height, or weight (p > 0.05).
  • Forward Head Angle (FHA) and Forward Shoulder Angle (FSA) differed significantly between NHP, IHP, and CHP groups
    • Tukey's post-hoc test indicated significant (p < 0.05) between NHP and IHP, and NHP and CHP with respect to FSA
  • NHP and IHP and NHP and CHP groups showed significant differences in UT and SA activation, but no significant differences found between IHP and CHP groups (p > 0.05)

Conclusions Patient's perception of ideal head posture (IHP), and correct head posture as cued by a professional (CHP), improved shoulder kinetics and movement patterns by altering Upper Trapezius and Serratus Anterior activation.Conclusions of the ResearchersForward head posture significantly increases upper trapezius and serratus anterior activation resulting in suboptimal scapular kinematics. Individuals who self-corrected their posture to what they believed to be "ideal", benefited immediately from improved scapular kinematics and muscle activation when performing an overhead shoulder elevation task.

Trapezius. Upper fibers are in orange, middle fibers are in red, and lower fibers are in purple.
Caption: Trapezius. Upper fibers are in orange, middle fibers are in red, and lower fibers are in purple.

By Anatomography - en:Anatomography (setting page of this image)., CC BY-SA 2.1 jp, https://commons.wikimedia.org/w/index.php?curid=22182550; Trapezius. Upper fibers are in orange, middle fibers are in red, and lower fibers are in purple.

Review & Commentary:

The current study provides additional support to the literature that forward head positioning influences muscular recruitment of serratus anterior (SA) and upper trapezius (UT) musculature. A simple postural correction, either to the subject's self-selected "ideal" head posture (IHP) or from cuing by a Physical Therapist (CHP), decreased muscle activity of the SA and UT . The authors posited that scapular kinematics subsequently improved from the sagittal plane head re-positioning in the IHP and CHP conditions.

The strength of the study lies in its simplicity. The authors repeated a loaded flexion task protocol previously performed by Thigpen et al. (1), adjusting the head positioning, and recording the muscle activity of the SCM, UT , LT , and SA . Muscular activity changes were recorded under the NHP, IHP, and CHP positions and the implications for clinical practice were discussed.

The current study did have limitations that should be acknowledged before application to clinical practice. First, the authors did not describe the study population demographics in their methodology, only suggesting that they met the inclusion criteria for forward head and rounded shoulder posture (FHRSP). Statistical analysis revealed no significant differences among the three head position groups with respect to age, sex, height, or weight (p > 0.05), but it is perplexing that they did not report the demographics of the subjects in the paper thus limiting its applicability. Second, the authors mentioned scapular kinematics in their conclusion as a reason why correction in the IHP and CHP group may have resulted in decreases in SA and UT activation; however, no scapular kinematic data was taken. Previous research has documented changes in scapular kinematics with FHRSP in an overhead shoulder elevation task; providing support for the authors assumption of altered scapular kinematics (1). It would have added additional strength to their methodology to include scapular kinematics data, matching the kinematics to head position and altered muscle activity. Third, the authors did not investigate cervical spine kinematics which could have added additional data to the consequences of FHRSP on bony anatomy, and potentially correlate with UT activity. Finally, the positions tested for maximum voluntary isometric contractions were not specified in the protocol, so it is unclear what positioning the subjects were in when each muscle group was tested.

Why is this study important?

The current study suggests that cuing better postural alignment may have immediate influence on muscular activity of the SA and UT . Although, further intervention may be necessary for resolution of symptoms and/or long-term improvement of postural alignment, this study suggests that patient's attempts to sit-up straighter, bring the head back over the shoulders, and/or maintain optimal head posture during exercise may have a positive affect on the quality of movement.

How does it affect practice?

When performing any activity or exercise, cuing for a neutral head position can instantly alter SA and UT activation patterns in individuals with FHRSP. Further, the current study results indicate that cueing for what the individual perceives as ideal head posture is just as effective as manual positioning with verbal cueing from an experienced Physical Therapist, which should give the human movement professional confidence in recommending that a patient correct their posture whenever possible during activities of daily living and home exercise programs. This simple adjustment may optimize periscapular muscle activity and allow for increased performance.

How does it relate to Brookbush Institute Content?

In those exhibiting Upper Body Dysfunction (UBD) and/or Cervical Dysfunction, forward head posture is commonly noted. In these dysfunctions the upper trapezius is commonly over-active, and serratus anterior under-active (2); however, correction of this posture may be best addressed by deep neck flexor activation . The role of the deep neck flexors is to reduce the cervical lordosis (resist excessive lordosis), stabilize the cervical spine, in essence, opposing the forward head position. This study suggests that the addition of deep neck flexor activation may be an important component to all individuals exhibiting changes in scapular kinematics who also exhibit forward posture, regardless of whether the patient is complaining about cervical, thoracic, scapular or shoulder pain. The current study also illustrates that simple cuing to restore excessive sagittal plane displacement of the head may facilitate better muscle firing patterns of periscapular muscles. Below are sample videos demonstrating release and activation exercises for the muscles noted in this article:

Brookbush Institute Videos:

Upper Trapezius Self-administered Static Release

Deep Cervical Flexor Isolated Activation (Longus Colli, Longus Capitis & Rectus Capitis Anterior)

Serratus Anterior Isolated Activation

Prone Cobra on Foam Roll (Activation for muscles of the scapula, thorax & deep cervical flexors)


  1. RESEARCH REVIEW: Thigpen CA, Padua DA, Michener LA, Guskiewicz K, Giuliani C, Keener JD, Stergiou N. (2010). Head and shoulder posture affect scapular mechanics and muscle activity in overhead tasks. Journal of Electromyography and Kinesiology. 20: 701-709.
  2. RESEARCH REVIEW: Helgadottir, H., Kristjansson, E., Einarsson, E., Karduna, A., & Jonsson, H. (2011). Altered activity of the serratus anterior during unilateral arm elevation in patients with cervical disorders. Journal of electromyography and kinesiology,21(6), 947-953.

© 2016 Brent Brookbush

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