The pectoralis muscles, comprised of the pectoralis major and minor, are essential for the dynamic movement and stabilization of the shoulder girdle. This article will dissect the intricate anatomy and biomechanics of these muscles, highlighting their critical role within the kinetic chain and their incorporation in the Motion Specific Release (MSR) framework.
We will examine the pectoralis major's influence on humeral movements and the pectoralis minor's effect on scapular positioning and respiratory function. The clinical implications of pectoralis dysfunction, including common presentations such as anterior shoulder pain and restricted range of motion. Moreover, we will introduce MSR techniques aimed at enhancing the function and coordination of these muscles, crucial for practitioners addressing complex shoulder conditions and optimizing thoracic mobility.
Article Index:
Anatomy & Biomechanics of the Pectoralis Muscles
The pectoralis major and minor muscles underpin the movement and stability of the anterior thoracic wall and shoulder girdle. Originating from the clavicle, sternum, and ribs, the pectoralis major converges into a tendon inserting on the humerus. This arrangement facilitates arm adduction, flexion, and internal rotation. The pectoralis minor extends from the third to fifth ribs to the coracoid process of the scapula, influencing scapular depression and protraction, crucial for respiration and shoulder function.
Origin and Insertion:
The pectoralis major's clavicular head originates from the medial half of the clavicle, and its sternocostal head from the sternum and upper six costal cartilages, converging to insert on the lateral lip of the bicipital groove of the humerus.
The pectoralis minor arises from the anterior surfaces of the third to fifth ribs and inserts into the medial border and superior surface of the coracoid process of the scapula.
Innervation:
Innervation of the pectoralis major is through the medial and lateral pectoral nerves, stemming from the brachial plexus.
The pectoralis minor is also supplied by the medial pectoral nerve, carrying fibers from the eighth cervical and first thoracic nerves (C8-T1), which is essential for its activation.
Biomechanical Role:
The pectoralis major is a prime mover in horizontal adduction and internal rotation of the arm, with the clavicular head aiding in arm flexion and the sternocostal head in extension from a flexed position.
The pectoralis minor stabilizes the scapula by drawing it anteroinferiorly against the thoracic wall, modulating scapulothoracic movements and impacting thoracic posture.
Biomechanical Dynamics:
Biomechanically, these muscles must coordinate with the deltoid, rotator cuff, and scapular stabilizers for efficient upper limb movement. The pectoralis major, through its large moment arm, significantly affects the force generation in movements like pushing and bench pressing.
The pectoralis minor's role in scapular kinematics is vital for maintaining the alignment of the glenohumeral joint during arm movements.
MSR Perspective:
From an MSR viewpoint, the pectoralis muscles are approached as integral components within the thoracic and shoulder kinetic chain. Imbalances or restrictions in these muscles can alter biomechanics, leading to issues such as shoulder impingement or thoracic outlet syndrome. MSR techniques are employed to address these dysfunctions, focusing on restoring the fascial and neuromuscular balance necessary for fluid upper body movements and postural integrity.
Motion Specific Release (MSR) Treatment
Initial Setup:
Patient Position: The patient lies supine to allow comprehensive access to both the pectoralis major and minor muscles, which are critical for various upper body activities, from office work to athletic endeavors in sports like swimming and golfing.
Practitioner Stance: The practitioner positions themselves to apply MSR techniques effectively, ensuring optimal reach and leverage for addressing the pectoral musculature. (See video)
Basic Technique:
Treatment: Identification of key anatomical landmarks begins the procedure. For the pectoralis major, focus is on the clavicular and sternocostal heads, recognizing their distinct contributions to shoulder mechanics.
Support Hand: The practitioner uses the opposite hand to control arm motion, guiding the muscle through its functional range to facilitate the release process.
Synchronization: Careful coordination of hands and controlled movements engage the pectoral muscles, emphasizing the integration of both heads during the release.
Pressure Application: Gradual, responsive pressure is applied to work into the muscle tissues, with communication ensuring patient comfort and effective release.
Technique:
Contact: A combination of hand positions, including the pads of fingers, or dorsal surface of hand, are utilized to address the muscle fibers from varied angles for a comprehensive treatment.
Combining Procedures:
Combined Actions: The inclusion of arm movements such as circumduction and internal-external rotations during treatment.
Pectoralis Release Procedures - MSR Demonstration:
In this video, Dr. Abelson demonstrates Motion Specific Release (MSR) procedures for releasing the Pectoralis Major & Minor Muscles.
Best Practices:
A bilateral, patient-centric approach is crucial, with attention to the individual's unique musculoskeletal dynamics. Emphasis is placed on treating both sides, acknowledging that restrictions typically involve both pectoralis muscles.
Kinetic Chains:
The practitioner is mindful of the pectoral muscles' role within the kinetic chain, appreciating their significance in upper limb and thoracic mechanics and ensuring a holistic treatment strategy.
Precautions:
Prioritizing safety, the practitioner navigates contraindications and secures informed consent before MSR application. Adjustments to pressure and movement are made in response to continuous patient feedback, ensuring a tailored and safe MSR experience.
Functional Kinetic Chains
The pectoralis major and minor muscles are integral to the functional kinetic chains of the upper body, orchestrating movements across the chest, shoulders, and arms. Understanding their synergy with adjacent structures is critical for a comprehensive grasp of their biomechanical and functional roles.
Direct Myofascial Connections:
The pectoralis muscles are deeply interconnected within the upper body's functional anatomy through substantial myofascial links:
Anterior Thoracic Fascia: This fascial layer envelops the pectoralis muscles, aligning their actions with the ribcage and scapular motions, affecting respiration and upper limb movements.
Intermuscular Septa: Fibrous partitions that delineate the pectoralis muscles from neighboring structures, such as the deltoids, facilitate coordinated movement and house neurovascular bundles.
Synergists:
Muscles that work in conjunction with the pectoralis group include:
Serratus Anterior: Assists in scapular motion and thoracic stability, harmonizing with the pectoralis minor during arm elevation and reaching tasks.
Rotator Cuff Muscles: Synergize with the pectoralis major, especially during movements requiring humeral stability and mobility.
Stabilizers:
Muscles that stabilize in concert with the pectoralis muscles are:
Trapezius Muscle: Forms a force-couple with the pectoralis minor, stabilizing the scapula against the thoracic wall, particularly in arm movements and overhead activities.
Rhomboids and Levator Scapulae: These muscles offer stabilization and balance to the pectoralis muscles' actions on the scapula, ensuring smooth shoulder girdle function.
Antagonists:
Muscles that act antagonistically to the pectoralis group:
Latissimus Dorsi: Opposes the pectoralis major by facilitating scapular retraction and extension, providing a counterforce in the posterior kinetic chain.
Posterior Deltoid: Balances the pectoralis major's actions during shoulder horizontal abduction and external rotation.
MSR Perspective:
From an MSR perspective, the pectoralis muscles are central elements in a complex biomechanical system. MSR techniques are designed to acknowledge and treat the interconnectedness within these kinetic chains. By understanding the myofascial and neuromuscular relationships involving the pectoralis muscles, MSR interventions can be tailored to address dysfunctions and reinforce the coordination of movements throughout the upper body.
Exercise
Effective pectoralis conditioning integrates mobility for full-range movement, strength for muscular power and endurance, and proprioception for sensory feedback and coordination.
4 Chest Stretches
Stretching the chest muscles is essential for maintaining flexibility and range of motion in the upper body, which is vital for activities that involve pushing, pulling, and lifting. Regular chest stretches can help alleviate postural issues and muscle tightness often caused by prolonged sitting and computer use, promoting better posture and reducing the risk of shoulder and neck discomfort.
Pectoral Muscle Release
Myofascial release of the pectoralis muscles is crucial for alleviating tension and restrictions within the chest that can impede shoulder mechanics and postural alignment. This therapeutic intervention enhances muscular flexibility, circulation, and the functional interplay between the pectorals and surrounding structures.
4 Compound Arm Exercises
Compound arm exercises effectively engage multiple muscle groups and joints concurrently, offering a comprehensive approach to upper body strength training. By utilizing the cooperative dynamics of muscles, tendons, and joints in the arms, these exercises deliver a thorough workout.
4 Cardinal Planes - Shoulder Stabilization Exercise
The 4 Cardinal Planes shoulder stabilization exercise works on proprioception, balance, and coordination for your shoulder and its surrounding muscles as it moves through various ranges of motion.
Conclusion
This analysis of the pectoralis major and minor muscles emphasizes their biomechanical relevance in shoulder girdle stability and movement. Incorporating Motion Specific Release (MSR) methodologies, the article bridges the gap between muscular anatomy and clinical application, offering essential insights for injury prevention and sports performance. The content aims to enhance practitioners' understanding of pectoral muscle function in various physical activities and its impact on overall musculoskeletal health.
DR. BRIAN ABELSON, DC. - The Author
Dr. Abelson's approach to musculoskeletal health care reflects a deep commitment to evidence-based practices and continuous learning. In his work at Kinetic Health in Calgary, Alberta, he focuses on integrating the latest research with a compassionate understanding of each patient's unique needs. As the Motion Specific Release (MSR) Treatment Systems developer, he views his role as both a practitioner and an educator, dedicated to sharing knowledge and techniques that can benefit the wider healthcare community. His ongoing efforts in teaching and practice aim to contribute positively to the field of musculoskeletal health, with a constant emphasis on patient-centered care and the collective advancement of treatment methods.
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ReferencesÂ
Abelson, B., Abelson, K., & Mylonas, E. (2018, February). A Practitioner's Guide to Motion Specific Release, Functional, Successful, Easy to Implement Techniques for Musculoskeletal Injuries (1st edition). Rowan Tree Books.
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Lewis, J. S., Wright, C., & Green, A. (2005). Subacromial impingement syndrome: The effect of changing posture on shoulder range of movement. Journal of Orthopaedic & Sports Physical Therapy, 35(2), 72-87.
Neumann, D. A. (2002). Shoulder complex. In Rehabilitation of the spine: A practitioner's manual (pp. 92-173). Lippincott Williams & Wilkins.
Sharkey, N. A., & Marder, R. A. (1995). The rotator cuff opposes superior translation of the humeral head. The American Journal of Sports Medicine, 23(3), 270-275.
Smith, J., Brunolli, J. (2017). Shoulder muscle balance and subacromial impingement syndrome. Manual Therapy, 22, 211-215.
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