Proximal attachments: Medial half of the Clavicle, the Sternum, costal cartilages of ribs 1-6, and the upper portion of the rectus abdominis sheath.

Distal attachment: Crest of the Greater Tubercle of the Humerus (Lateral lip of the bicipital groove)

Actions:

Pec Major is the prime mover for adduction of the humerus and can also perform humeral flexion up to 90 degrees, internal rotation, and horizontal adduction.

When the arm is overhead, the pec major can perform extension (pull the arm back down) until about 90 degrees

Some modern-day examples of the action of pec major include:

• Throwing a ball from overhead
• Giving a hug
• Throwing a punch

Unique Features:

The Pectoralis Major is the largest muscle on the anterior chest. It can be divided into two heads:

Clavicular head: aiding in flexion, adduction, horizontal adduction and internal rotation.

Sternocostal head: aiding in extension from overhead, adduction, horizontal adduction, and internal rotation. This muscle also is an assisting muscle for inspiration (breathing in), especially during physical activity.

It’s rare, but this is a muscle that can tear at the insertion and even cause an avulsion (where the periosteum of the bone is pulled off). You will usually see this in athletes who lift heavy, most often injured during bench pressing.

Pec major is prone to hypertonicity and adaptively shortening, clients will often present with rounded, internally rotated shoulders. The wall slide assessment can be a great tool in determining if Pec Major is hypertonic or over-active.

Trigger Point and Pain Referral Patterns:

The referral pain pattern for pec major is local and sometimes presents in the anterior deltoid region.

Images sources from Biodigitalhuman @ human.biodigital.com