Dominic Stone
The pectoral muscles, commonly referred to as pecs, are a vital component of the upper body musculature. They are made up of the pectoralis major, pectoralis minor, and the serratus anterior. The pectoralis major is the largest muscle of the anterior chest wall and has two heads, the clavicular and the sternocostal, which reference their area of origin. The pectoralis minor lies underneath its larger counterpart and both muscles form part of the anterior wall of the axilla region. The serratus anterior is located more laterally in the chest wall and forms the medial border of the axilla region. The pectoral muscles are crucial in various movements, including pushing, lifting, and stabilizing the shoulders and arms. They also work with other muscles around the shoulder joint to maintain stability and proper alignment.
| Characteristics | Values |
|---|---|
| Common name | Pecs |
| Scientific name | Pectoralis major, pectoralis minor |
| Muscle group | Pectoral region |
| Muscle shape | Thick, fan-shaped |
| Muscle function | Adducts and medially rotates the upper limb, draws the scapula anteroinferiorly, stabilises the scapula |
| Innervation | Lateral and medial pectoral nerves |
| Attachments | Anterior sternum, clavicular head, sternal end of rib 6, superior six costal cartilages, aponeurosis of the external oblique, intertubercular sulcus of the humerus |
| Exercises | Flat barbell bench press, flat dumbbell bench press, dumbbell fly |
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What You'll Learn
Pectoralis major
The pectoralis major is the superior most and largest muscle of the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. The pectoralis major is the most superficial muscle in the pectoral region, which also includes the pectoralis minor and the serratus anterior. The pectoralis minor lies underneath the pectoralis major and is much thinner and triangular in shape.
The pectoralis major has two heads, the clavicular and the sternocostal, which reference their area of origin. The clavicular head allows for the flexion of the humerus, as seen when lifting a glass for a toast. The muscle fibres attaching to the sternocostal head permit the horizontal and vertical adduction, extension, and internal rotation of the upper extremity.
The pectoralis major can be tested for strength and length. To test for strength, the examiner holds the opposite shoulder firmly on the table while the subject transversely adducts the arm at the glenohumeral joint against resistance. To test for length, the subject lies supine with the knees bent and the low back flat on the table. The examiner places the subject's arm in horizontal abduction, with the elbow extended and the shoulder in lateral rotation.
The pectoralis major can be strengthened through various exercises, including pressing exercises such as the flat barbell bench press and the flat dumbbell bench press. These exercises involve the individual lying supine on a bench with their feet flat on the ground and utilising either a barbell or a pair of dumbbells.
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Pectoralis minor
The pectoralis minor is a thin, triangular muscle located under the pectoralis major. It is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. The pectoralis minor originates from the margins of the third to fifth ribs, near the costal cartilages, and the fibres pass upward and laterally to insert into the medial border and superior surface of the coracoid process of the scapula. It is crucial for stabilising the scapula by pulling it downward and anteriorly against the thoracic wall.
The pectoralis minor is also an accessory muscle of respiration. It creates a passage between the ribs for the brachial plexus, the subclavian artery, and vein. If the pectoralis minor is shortened or tightened, it can cause abnormal tension, negatively affecting the Scapulohumeral Rhythm and leading to thoracic outlet syndrome. This syndrome involves impingement on the cords of the brachial plexus and axillary blood vessels, resulting in shoulder impingement and pain, numbness, and tingling in the arm and hand.
The pectoralis minor serves as a reference point for the three divisions of the axillary artery. The medial pectoral nerve pierces the muscle and the clavipectoral fascia, forming a 'bridge' for structures passing into the upper limb from the thorax. Axillary nodes are classified according to their positions relative to the pectoralis minor, with Level 1 being lateral, Level 2 deep, and Level 3 medial.
To palpate the pectoralis minor, one can place a finger in the axilla and push towards the coracoid process of the scapula. Exercises that selectively activate the serratus anterior while minimising pectoralis minor activity include the serratus punch exercise and the modified push-up plus exercise.
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Serratus anterior
The serratus anterior (SA) is a thin, fan-shaped sheet of muscle that originates from the outer surface of the first to eighth or ninth ribs at the lateral wall of the thorax. It then wraps around the ribcage, passing beneath the scapula to insert into the scapula's underside on its medial border. The serratus anterior is divided into three parts: superior, intermedius, and inferior, with the latter being the most powerful and prominent part.
The serratus anterior is a key scapular stabiliser, keeping the shoulder blades against the ribcage at rest and during movement. It is the prime mover in scapular protraction and scapular upward rotation, acting in concert with the upper and lower fibres of the trapezius muscle. This allows for overhead lifting and anteversion and protraction of the arm, such as when throwing a punch. For this reason, the serratus anterior is also known as the "boxer's muscle" or the "big swing muscle".
The serratus anterior is easily palpable between the pectoralis major and latissimus dorsi muscles. The muscle is supplied with oxygenated blood by the lateral thoracic artery, superior thoracic artery, and thoracodorsal artery. The long thoracic nerve, which arises from C5 to C7 nerve roots of the brachial plexus, is responsible for the innervation of the serratus anterior.
The most common causes of serratus anterior muscle pain include tension, stress, and overuse. This pain may also result from serratus anterior myofascial pain syndrome (SAMPS), a rare myofascial pain syndrome.
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Shoulder stability
The pectoralis major is the largest muscle of the anterior chest wall. It is thick and fan-shaped, lying underneath the breast tissue. There are two heads to the pectoralis major: the clavicular and the sternocostal. The pectoralis minor is a thinner, triangular muscle that resides below the pectoralis major.
The pectoralis minor is crucial for shoulder stability. It attaches to the third, fourth, and fifth ribs near the costal cartilage and inserts into the coracoid process (part of the scapula or wing bone). The pectoralis minor can become tight from activities performed with poor posture, such as working at a computer, driving, or reaching forward. This can cause muscle imbalances when using the shoulders, leading to pain and potential injury.
To improve shoulder stability, it is important to stretch and foam roll the pectoralis minor to improve posture. This can be done through exercises such as standing in a doorway with elbows bent and forearms resting on each side of the door frame, then stepping forward with one foot to stretch the chest and arms. Another exercise is to lie on your stomach with your injured arm hanging over the side and slowly raise it to eye level.
Additionally, strengthening the muscles that support the shoulder can help stabilize the joint. This can be done through pressing exercises such as the flat barbell bench press or the flat dumbbell bench press, which utilize the pectoralis major muscle. It is also important to stretch the muscles that you strengthen to restore the range of motion and prevent injury.
Overall, creating and maintaining balance between the muscles in the front and back of the shoulders is key to achieving stable and healthy shoulders.
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Orthopaedic issues
The pectoralis muscle is located on the front of the chest and is attached to the bone of the upper arm or shoulder by tendons. The pectoralis major is the superior most and largest muscle of the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. The pectoralis major tendon rupture is a rare shoulder injury, most commonly seen in weightlifters. However, it has become more prevalent over the past 20 years due to increased participation in weight lifting and sports.
Pectoralis major ruptures are uncommon injuries that occur when the pectoralis tendon tears away from the bone. They were first described in 1822 when an apprentice butcher injured himself at work and subsequently died from a likely infected hematoma. Throughout the 1900s, only case reports were published, with a meta-analysis in 2000 finding only 150 cases of PM ruptures, with a mean age at the time of rupture being 28 years. The majority of these cases were due to work injuries, but since 1972, nearly all reported cases have been related to sports injuries.
PM ruptures can be defined as either total or near-total and most commonly occur at the tendon insertion or the musculotendinous junction. These injuries typically occur in males between the ages of 20 and 40 years, and patients often present with localized swelling and ecchymosis, muscular deformity, thinning of the anterior axillary fold, and weakness in adduction and internal rotation of the affected arm. The injury occurs when there is excessive tension on a maximally contracted muscle, and patients will typically report a sudden pop or tearing sensation.
Diagnosis and treatment
A pectoralis tear can vary in the level of pain, but it is typically very painful. There can be severe bruising in the chest, shoulder, and arm, and there may be a gap in the muscle tissue visible with a tear. Using or lifting the arm on the side of the torn pectoral would likely be painful and weak, with swelling in the chest and shoulder region. X-rays, ultrasounds, and magnetic resonance imaging (MRI) scans can be used to confirm the diagnosis.
Treatment options depend on the severity of the injury and the individual's specific circumstances. For mild to moderate pectoral strains or ruptures, the initial treatment approach is often rest, ice, compression, and elevation (RICE). Physical therapy may also be recommended to limit scar tissue and flexibility issues, and progressive strength training is typically part of the recovery process as swelling and pain decrease. In the case of a complete tear of the tendon away from the bone, surgical repair is usually necessary to return arm strength to near normal levels.
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Frequently asked questions
Pecs, or the pectoral muscles, are a vital component of the upper body musculature. They are responsible for various movements, including pushing, lifting, and stabilizing the shoulders and arms.
There are three muscles in the pectoral region: pectoralis major, pectoralis minor, and serratus anterior. The pectoralis major is the largest and most superior muscle of the anterior chest wall. The pectoralis minor lies underneath the pectoralis major and is much thinner and triangular in shape. The serratus anterior is located more laterally in the chest wall and helps move the scapula forward around the torso, as when throwing a punch.
Many exercises focus on the pectoralis muscle, including pressing exercises such as the flat barbell bench press and the flat dumbbell bench press. In these exercises, the individual lies supine on a bench with their feet flat on the ground and uses weights to strengthen the pecs.
