teres major and minor

Daniel Parker

2 min read

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14-03-2025

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The teres major and minor muscles are two important muscles located in the posterior (back) of the shoulder. While often grouped together due to their proximity and similar functions, they have distinct origins, insertions, and actions. Understanding their roles is crucial for anyone interested in anatomy, fitness, or physical therapy.

Anatomy of the Teres Major Muscle

The teres major is a larger, more powerful muscle compared to its neighbor.

Origin and Insertion

• Origin: Inferior (lower) angle of the scapula (shoulder blade).
• Insertion: Medial lip of the intertubercular groove of the humerus (upper arm bone).

Actions

The teres major's primary actions are:

• Shoulder extension: Pulling the arm backward.
• Shoulder adduction: Moving the arm towards the midline of the body.
• Medial rotation of the shoulder: Rotating the arm inward.

Think of the teres major as a powerful "helper" muscle in many arm movements, contributing to strength and stability.

Anatomy of the Teres Minor Muscle

The teres minor, as its name suggests, is smaller than the teres major.

Origin and Insertion

• Origin: Lateral border of the scapula.
• Insertion: Greater tubercle of the humerus.

Actions

The teres minor plays a crucial role in:

• Shoulder external rotation: Rotating the arm outward.
• Shoulder horizontal abduction: Moving the arm away from the body in a horizontal plane.
• Shoulder extension: A lesser role compared to the teres major.

It works in synergy with other rotator cuff muscles to maintain shoulder stability and control movement.

Teres Major and Minor: Working Together

Although distinct, the teres major and minor muscles often work together to perform various shoulder movements. They contribute to the complex interplay of muscles responsible for the remarkable range of motion in the shoulder joint. Understanding their combined actions is essential for effective rehabilitation and injury prevention.

Synergistic Actions

Both muscles contribute to shoulder extension, highlighting their collaborative role in powerful movements like pulling or rowing. However, their opposing roles in medial and lateral rotation show the nuanced control they provide.

Importance in Athletic Performance

These muscles are particularly important for athletes involved in sports requiring significant shoulder movement, such as swimming, tennis, baseball, and weightlifting. Strong teres muscles contribute to power, stability, and injury prevention.

Common Injuries Affecting the Teres Muscles

Although less frequently injured than other shoulder muscles, the teres major and minor can be affected by:

• Strains: Overuse or sudden forceful movements can strain these muscles, leading to pain and reduced function.
• Rotator Cuff Tears: These tears often involve the teres minor, given its role in the rotator cuff.
• Shoulder Impingement: Inflammation and compression of structures within the shoulder joint can affect the teres muscles.

Exercises to Strengthen Teres Major and Minor

Strengthening these muscles can improve shoulder stability and reduce injury risk. Here are some effective exercises:

• Bent-Over Rows: Targets both muscles effectively.
• Pull-Ups: Excellent for overall back and shoulder strength, including teres muscles.
• Face Pulls: Specifically targets the teres minor and posterior deltoids.
• External Rotation Exercises: Use resistance bands or weights to isolate the external rotation action of the teres minor.

Remember to consult with a healthcare professional or certified personal trainer before starting any new exercise program. Proper form is crucial to prevent injuries.

Conclusion

The teres major and minor muscles are essential components of the shoulder complex. Understanding their individual roles and collaborative efforts provides a more complete picture of shoulder mechanics. Maintaining their strength and health is crucial for optimal shoulder function and injury prevention. Remember to incorporate exercises that target these muscles as part of a well-rounded fitness routine.