Triceps Brachii Muscle: Anatomy, Functions, and Training

What is the function of the triceps brachii muscle?

The triceps brachii is the primary extensor of the elbow joint, responsible for straightening the arm, and its long head also contributes to shoulder extension and adduction.

Anatomy of the Triceps Brachii

The triceps brachii, meaning "three-headed arm muscle," is a large, thick muscle located on the posterior aspect of the upper arm. It originates from three distinct heads and converges into a common tendon before inserting into the elbow.

• Long Head: Originates from the infraglenoid tubercle of the scapula (shoulder blade). Being the only head that crosses the shoulder joint, it has actions on both the elbow and shoulder.
• Lateral Head: Originates from the posterior surface of the humerus, superior to the radial groove.
• Medial Head: Originates from the posterior surface of the humerus, inferior to the radial groove, and is largely covered by the long and lateral heads.

All three heads converge to form a strong tendon that inserts primarily into the olecranon process of the ulna, a prominent bony projection at the back of the elbow.

Primary Function: Elbow Extension

The most critical and well-known function of the triceps brachii is elbow extension. This action involves straightening the arm at the elbow joint, moving the forearm away from the upper arm.

• Mechanism: When the triceps contracts, it pulls on the olecranon process, causing the ulna to pivot around the trochlea of the humerus, thereby extending the elbow.
• Role of Each Head:
  • The medial head is considered the "workhorse" of the triceps, active in all forms of elbow extension, particularly during low-resistance movements.
  • The lateral head is recruited strongly during movements requiring greater force and against higher resistance.
  • The long head contributes significantly to powerful elbow extension, especially when the shoulder is flexed (arm overhead).

This function is vital for a wide range of daily activities and athletic movements, including pushing, throwing, and stabilizing the arm.

Secondary Functions: Shoulder Joint Involvement

Due to the unique origin of its long head on the scapula, the triceps brachii also plays a significant role in movements at the shoulder joint.

• Shoulder Extension: The long head can assist in extending the shoulder, pulling the arm backward from a flexed position. This occurs when the arm moves posteriorly, such as during the downward phase of a pull-over or when pushing off from a surface.
• Shoulder Adduction: The long head can also aid in adduction of the shoulder, pulling the arm towards the midline of the body. This action helps to stabilize the shoulder joint, particularly when the arm is abducted (moved away from the body).
• Stabilization: The long head's attachment to the scapula also contributes to the stability of the glenohumeral joint (shoulder joint), helping to keep the head of the humerus centered in the shallow glenoid cavity.

Synergists and Antagonists

Understanding the muscles that work with or against the triceps helps in comprehending its full role in movement.

• Synergists (Assisting Muscles):
  • Anconeus: A small muscle located near the elbow, it assists the triceps in elbow extension and helps to stabilize the elbow joint during pronation and supination of the forearm.
• Antagonists (Opposing Muscles):
  • Biceps Brachii: The primary flexor of the elbow and supinator of the forearm.
  • Brachialis: Considered the "pure" elbow flexor, as it only crosses the elbow joint.
  • Brachioradialis: An elbow flexor that is particularly active when the forearm is in a neutral position (thumb up).

Practical Implications for Training

To effectively strengthen the triceps brachii and maximize its functional capacity, it's important to incorporate exercises that target all three heads.

• Varying Hand Positions: Different grips and hand positions can subtly alter the emphasis on each head.
• Arm Angles:
  • Overhead movements (e.g., overhead triceps extensions, overhead press) place a greater stretch and emphasis on the long head due to its involvement in shoulder extension.
  • Pressing movements (e.g., bench press, push-ups) and pushdowns tend to activate the lateral and medial heads more directly for powerful elbow extension.
• Compound vs. Isolation:
  • Compound exercises like bench presses, overhead presses, and dips work the triceps alongside other major muscle groups, building overall pushing strength.
  • Isolation exercises such as triceps pushdowns, skullcrushers, and overhead triceps extensions allow for more focused development of the triceps.

Common Triceps Exercises

Incorporating a variety of exercises ensures comprehensive development of the triceps.

• Compound Movements:
  • Bench Press (Close-Grip): Emphasizes the triceps more than a standard grip.
  • Overhead Press: Engages the triceps significantly, especially in the lockout phase.
  • Dips: An excellent bodyweight exercise for overall triceps development.
  • Push-ups: A fundamental exercise that heavily recruits the triceps.
• Isolation Movements:
  • Triceps Pushdowns (Rope or Bar): Versatile for targeting different heads based on grip.
  • Overhead Triceps Extensions (Dumbbell or Cable): Excellent for stretching and engaging the long head.
  • Skullcrushers (Lying Triceps Extensions): Direct elbow extension exercise, typically with a barbell or dumbbells.
  • Kickbacks (Dumbbell): Focuses on the contraction of the triceps in the fully extended position.

Conclusion

The triceps brachii is a powerful and essential muscle for upper body function. Its primary role in elbow extension is critical for all pushing movements and arm straightening, while the long head's contribution to shoulder stability, extension, and adduction further underscores its importance. By understanding its anatomy and functions, individuals can design more effective training programs to enhance strength, power, and overall arm function, contributing to both athletic performance and daily activities.