What is pectoralis major muscle?

Pectoralis Major Muscle

Introduction

The pectoralis major is one of the most prominent and powerful muscles of the anterior chest wall. Recognizable as the major contributor to the chest’s contour, it plays an essential role in upper limb movement and shoulder joint stability. Clinically, this muscle is crucial in strength training, rehabilitation, and postural function, particularly in activities involving pushing or lifting. Understanding the structure and function of the pectoralis major is vital for physical therapists, clinicians, and fitness professionals.

Anatomy of Pectoralis Major

Origin

The pectoralis major has two distinct heads:

• Clavicular head: originates from the anterior surface of the medial half of the clavicle.

• Sternocostal head: arises from the anterior surface of the sternum, the upper six costal cartilages, and the aponeurosis of the external oblique muscle.

Insertion

The muscle fibers converge to insert into the lateral lip of the intertubercular sulcus (bicipital groove) of the humerus.

Nerve Supply

The pectoralis major is innervated by:

• Lateral pectoral nerve (C5–C7)

• Medial pectoral nerve (C8–T1)

The medial pectoral nerve often pierces the pectoralis minor to innervate the deep surfaces of the pectoralis major.

Blood Supply

• Thoracoacromial artery (pectoral branch)

• Lateral thoracic artery

Function

The pectoralis major is responsible for multiple movements involving the shoulder joint:

• Adduction of the arm

• Medial rotation of the humerus

• Flexion of the shoulder (clavicular head)

• Extension of a flexed arm (sternocostal head)

In functional tasks such as climbing, pushing, or lifting, the pectoralis major provides substantial force and stability.

Clinical Assessment

Palpation

• Position: Patient supine or seated.

• Procedure: Ask the patient to push their hands together in a prayer position or press forward against resistance.

• Palpate across the chest just below the clavicle and along the anterior axillary fold.

Muscle Power Testing

• Clavicular head: Test shoulder flexion from 0° to 60° against resistance.

• Sternocostal head: Test shoulder adduction from an abducted position against resistance.

Muscle Length Testing

• Position the patient supine, arm abducted to 90°, and elbow flexed.

• Allow the arm to drop below the horizontal level of the table; limited drop suggests tightness in the pectoralis major.

Therapeutic Exercises

Strengthening Exercises

1. Chest Press (Bench Press)

   • Patient Position: Supine on a flat bench.

   • Procedure: Push the barbell or dumbbells vertically from the chest to full elbow extension.

2. Push-Ups

   • Patient Position: Prone with hands placed shoulder-width apart.

   • Procedure: Lower and lift the body by flexing and extending the elbows.

3. Cable Cross-Over

   • Patient Position: Standing between two high pulleys.

   • Procedure: Pull the handles downward and medially to cross hands in front of the chest.

Stretching Exercises

1. Doorway Stretch

   • Patient Position: Standing in a doorway with arms abducted to 90° and elbows flexed.

   • Procedure: Lean forward to stretch the anterior chest muscles.

2. Supine Arm Drop

   • Patient Position: Lying supine with arms hanging off the side of the table.

   • Procedure: Let the arms drop passively to stretch the muscle fibers.

Trigger Points and Referred Pain

Trigger points in the pectoralis major can develop due to repetitive overuse, stress, or poor posture. Common referred pain areas include:

• Anterior shoulder region

• Chest wall mimicking cardiac pain

• Medial arm and forearm

Trigger points can be treated with:

• Manual therapy

• Dry needling

• Stretching combined with heat therapy

Related Injuries and Conditions

• Pectoralis Major Tear or Rupture: Typically occurs during heavy weightlifting, particularly during eccentric contraction in bench pressing.

• Myofascial Pain Syndrome: Chronic pain condition involving trigger points.

• Postural Syndrome: Tightness of pectoralis major contributing to rounded shoulders and forward head posture.

• Breast Surgery Rehabilitation: The muscle may be involved in reconstructive procedures or affected by scarring.

FAQs

1. What are the signs of a torn pectoralis major?
Symptoms include sudden pain, bruising, and weakness during chest exercises. A visible deformity or gap may appear in the muscle.

2. How can I strengthen my pectoralis major without weights?
Bodyweight exercises like push-ups, incline push-ups, and wall presses are effective.

3. Can pectoralis major tightness affect breathing?
Yes, especially if the tightness impairs rib cage expansion or posture.

4. What causes trigger points in the pectoralis major?
Prolonged poor posture, heavy lifting, and emotional stress can contribute.

5. Can women benefit from pectoralis major exercises?
Absolutely. Strengthening this muscle improves posture, supports breast tissue, and enhances upper body function.

References

1. Neumann DA. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed. Elsevier; 2017. Available from: https://www.elsevier.com/books/kinesiology-of-the-musculoskeletal-system/neumann/978-0-323-39378-4

2. Standring S, ed. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. Elsevier; 2020. Available from https://www.elsevier.com/books/grays-anatomy/standring/978-0-7020-7705-0

3. Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function, with Posture and Pain. 5th ed. Lippincott Williams & Wilkins; 2005. Available from: https://shop.lww.com/Muscles-Testing-and-Function--with-Posture-and-Pain/p/9780781747806

4. Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual. Vol. 1. Lippincott Williams & Wilkins; 1999. Available from: https://www.sciencedirect.com/book/9780683083637/myofascial-pain-and-dysfunction

5. Clarkson HM. Musculoskeletal Assessment: Joint Range of Motion and Manual Muscle Strength. 3rd ed. Lippincott Williams & Wilkins; 2012. Available from: https://shop.lww.com/Musculoskeletal-Assessment/p/9781451117135