Research Review: Effect of Pectoralis Minor Manual Therapy and Stretching on Rounded Shoulder Posture and Lower Trapezius Strength
By Nicholas Rolnick SPT, MS, CSCS
Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS
Original Citation: Wong CK, Coleman D, diPersia V, Song J, Wright D. (2010). The effects of manual treatment on rounded-shoulder posture, and associated muscle strength. Journal of Bodywork & Movement Therapies. 14: 326-333. Link to Abstract
Why is this relevant?:
Previous studies show rounded-shoulder posture to be associated with scapular dysfunction (1-3). Individuals exhibiting this dysfunction commonly have adaptive shortening of the pectoralis minor, contributing to changes in resting and dynamic scapular position (4). Left unaddressed, postural dysfunction predisposes individuals to numerous shoulder pathologies from subacromial impingement, to degenerative rotator cuff pathology, to loss of force production of the musculature surrounding the glenohumeral joint (3). The current study sought to determine whether or not manual therapy and stretching of pectoralis minor reduces rounded-shoulder posture and increases lower trapezius strength in healthy 20- to 40-year old individuals.
Study Summary
| Study Design | Descriptive - Experimental |
| Level of Evidence | Level IB: Evidence from a Single Blinded RCT |
| Subject Demographics |
|
| Outcome Measures |
|
| Results |
|
| Conclusions | Manual therapy and stretching intervention of the pectoralis minor muscle resulted in significantly decreased rounded shoulder posture over two weeks compared to the control condition of placebo touch and stretching of the pectoralis major muscle but both conditions resulted in increased lower trapezius strength after the two-week follow-up. |
| Conclusions of the Researchers | Soft tissue mobilization and stretching of the pectoralis minor muscle can reduce rounded shoulder posture and increase lower trapezius strength. Rounded shoulder postural assessment measurements taken in supine with a 2.5 cm threshold may not be a sensitive measure to detect dysfunction of the pectoralis minor muscle. |
Review & Commentary:
There have been numerous research studies investigating the role of the pectoralis minor on scapulothoracic, scapulohumeral, and glenohumeral dysfunction (1-3, 5). In a systematic review of shoulder pathologies, Seitz et al. (2011) included pectoralis minor length as an extrinsic anatomical and biomechanical factor, leading to altered scapular kinematics and degenerative rotator cuff tears (3). Pectoralis minor acts as an anterior tipper and a downward rotator of the scapulothoracic joint and in turn functions as an antagonist to the serratus anterior . Rounded shoulder posture (RSP) has commonly been associated with pectoralis minor and serratus anterior dysfunction, posterior shoulder tightness, and thoracic kyphosis producing deficits in glenohumeral range of motion (hence the excessive forward lean in the overhead squat assessment ) (2). However, due to its adaptively shortened position in rounded shoulder posture, it has been hypothesized that this is one of the main causes of RSP (2,5). One study on RSP utilized a scapular posterior tilt exercise and a pectoralis minor stretching protocol and found that it reduced RSP more than a scapular posterior tilt exercise alone, implicating the pectoralis minor ’s relationship to shoulder kinematics and posture (2).
Wong’s (2010) study exhibited a strong research design as well as an experimental protocol that is commonly performed in the clinical setting. The study utilized a randomized and blinded design that minimized bias. One therapist (who was board-certified in orthopedics) performed all of the soft tissue mobilizations on pectoralis minor , minimizing any confounding treatment effects of the experimental group. For the control group, placebo touch was defined as passive placement of the fingers over the pectoralis major (over the location of pectoralis minor ) without applying tension or creating movement. In assigning treatment groups, the authors had adequate inclusion and exclusion criteria for the hypothesis that was investigated. Randomizing the participants in the control and experimental group strengthened their methodology and while in intervention studies like this one, full randomization of the researcher and participants is not possible, the authors minimized bias by having a single therapist perform the treatment. It is worth noting, that the study did not report whether the therapist who performed the treatment was blinded when the data was collected and interpreted. Furthermore, a two-tailed power analysis (set at 80%) was performed with a Z of 0.05 and common standard deviations based on previously performed research on RSP and lower trapezius strength manual muscle testing to determine the minimum sample size needed to show significant change. In addition to the strong methodology, the current study implemented a treatment approach that is commonly performed in the clinical setting to address RSP. Therefore, the outcome of the treatment group is more indicative of real-life outcomes in the clinic in individuals with RSP and otherwise healthy shoulders.
As a secondary observation, the authors concluded that their assessment of RSP, the supine pectoralis minor test, is not sensitive enough to predict dysfunction when set at 2.5 cm. This conclusion is in agreement with previous research (6-7). Clusters of tests should be performed to assess pectoralis minor length as it is only one contributing factor for RSP.
Another important result from the experiment indicated that lower trapezius strength was statistically increased in both conditions immediately post-intervention and after the two-week follow-up. Based on length-tension and principles of altered reciprocal inhibition, the lower trapezius strength should not have changed in the placebo condition as pectoralis major is not a direct antagonist. The stretch performed in the placebo condition stretched the clavicular head of the pectoralis major (considered a shoulder flexor, adductor, and internal rotator) which is commonly shortened in the RSP dysfunction. Restoring length to the clavicular head may have allowed for indirect facilitation of the lower trapezius muscle by reducing passive tension during the testing position at160 degrees of flexion and abduction. It was not specified what position the forearm was positioned. It could also be proposed that the subjects familiarized themselves with the testing procedure and were better able to recruit the desired muscle after the allotted trials.
There are limitations to the current research study that may implicate the need for further research before drawing conclusions to be implemented into clinical practice. First, while it is a strength of the study that participants’ shoulders were randomized (25 in the control group and 31 in the experimental group), the individuals who received both a placebo treatment and an experimental treatment (total of 19 participants, or 38 shoulders) may have felt a difference and responded differently based on their beliefs of which was more effective. The authors’ concluded that these group assignments did not influence experimental results as the Mann-Whitney U test ( p > 0.05) was not significant. It should be mentioned that although it was not statistically significant, adherence to the different protocols could be influenced by group assignment. Second, individuals (6) who had both shoulders randomized into the experimental group had greater (statistically significant p < 0.05 on Friedman’s test) changes in RSP than the three individuals who had both shoulders in the control group. The authors concluded that this disparity could contest that each shoulder should not be considered as a separate entity, as was performed in the study. Research supports the assertion that treatment of one side of the body may influence muscle activity on the other side, although this study was an exercise-only EMG study on PNF patterns in the lower extremity (8). Third, while the pectoralis minor soft tissue mobilization was performed in conjunction with a stretching technique as would be done in a clinical setting, it is impossible to conclude whether or not it was the mobilization or stretching that improved RSP and lower trapezius strength. Future research should investigate pectoralis minor soft tissue massage compared with a pectoralis minor stretch on RSP and lower trapezius strength.
Why is this study important?
The current study illustrated that a single 3-minute session of manual therapy and stretching, with the intent to release and lengthen the pectoralis minor can reduce rounded shoulder posture (RSP) for at least two weeks and increase lower trapezius strength.
The study also added to the developing body or research on assessment techniques, indicating that the supine pectoralis minor length test may not be as sensitive as previously thought (6-7). When determining pectoralis minor length, a cluster of tests should be performed and interpreted before performing a pectoralis minor intervention.
How does it affect practice?
Rounded-shoulder posture is a common postural dysfunction seen in the clinical setting. In this dysfunction, the pectoralis minor is commonly thought to contribute to excessive anterior tipping and internal rotation of the scapula, changing resting and dynamic scapular kinematics due to changes in resting length and by altering length-tension relationships and activity of the muscles surrounding the scapulothoracic complex. Frequently, serratus anterior and lower trapezius muscles are long and under-active. The current study illustrates that one session of manual therapy focusing on releasing pectoralis minor and a regimen of pectoralis minor stretching decreased rounded shoulder posture and increased lower trapezius strength for two weeks. Integrating pectoralis minor self-release techniques into clinical practice can help to restore proper posture and encourage optimal length-tension relationships of the scapulothoracic complex, including the lower trapezius . Although it wasn’t measured in this study, it can be reasonably assumed that serratus anterior activity would increase concurrently with a pectoralis minor release as they are functional antagonists.
How does it relate to Brookbush Institute Content?
The Brookbush Institute's predictive model of postural dysfunction, Upper Body Dysfunction (UBD) includes the altered scapulothoracic mechanics described in this study, including adaptive shortening and over-activity of the pectoralis minor and under-activity and weakness of the lower trapezius . This model reasons further that all muscles, joints, fascia, and potentially nerves of the scapulothoracic and glenohumeral joints may be affected. The Brookbush Institute’s approach to UBD involves releasing over-active muscles (including the pectoralis minor ), mobilizing joints exhibiting arthrokinematic dysfunction, lengthening short structure, and activating and integrating long and under-active muscles to restore optimal motion. It is a tenant of the Brookbush Institute, that the "completeness" of an intervention (addressing all structures exhibiting maladaptive change) will contribute to the efficacy and carry-over of any intervention. This study is an important step toward evidence-based intervention for the correction of postural dysfunction and the resolution of symptoms. The videos below demonstrate pectoralis minor release techniques:
Brookbush Institute videos
Pectoralis Minor Self-Administered Static Release
Pectoralis Minor Manual Release
Bibliography:
- Burkhart SS, Morgan CD, Kibler WB. (2000). Shoulder injuries in overhead athletes: the “dead arm” revisited. Clinics in Sports Medicine. 19(1): 125-158.
- Lee, J, Cynn H, Yoon T, Ko C, Choi W, et al. (2015). The effect of scapular posterior tilt exercise, pectoralis minor stretching, and shoulder brace on scapular alignment and muscles activity in subjects with round-shoulder posture. Journal of Electromyography and Kinesiology. 25:107-114.
- Seitz AL, McClure PW, Finucane S, Boardman III ND, Michener LA. (2011). Mechanisms of rotator cuff tendinopathy: intrinsic, extrinsic, or both?. Clinical Biomechanics. 1-12.
- Thigpin CA et al. (2010). Head and shoulder posture affects scapular mechanics and muscle activity in overhead tasks. Journal of Electromyography and Kinesiology. 20:701-709.
- Wong CK, Coleman D, diPersia V, Song J, Wright D. (2010). The effects of manual treatment on rounded-shoulder posture, and associated muscle strength. Journal of Bodywork & Movement Therapies. 14: 326-333.
- Lewis JS, Valentine RE. (2007). The pectoralis minor length test: a study of the intra-rater reliability and diagnostic accuracy in subjects with and without shoulder symptoms. BMC Musculoskeletal Disorders. 8: 64-73.
- Weber C, Enzler M, Wieser K, Swanenburg J. (2015). Validation of the pectoralis minor length test: a novel approach. Manual Therapy. 1-6.
- Yoo B, et al. (2013). The effects of abdominal hollowing in lower-limb pnf pattern training on the activation of contralateral muscles. Phys Ther. Sci. 25(10): 1335-8.©
2015 Brent Brookbush
Questions, comments, and criticisms are welcomed and encouraged.