Triceps Brachii – Anatomy Breakdown

Written By Austin Treadwell

Treadwell, DPT | Muscle by Muscle Series

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Watch on YouTube: Triceps Brachii – Anatomy Breakdown

In this episode, Dr. Austin Treadwell, DPT breaks down the Triceps Brachii — the three-headed powerhouse of elbow extension and one of the most overlooked players in shoulder stability and upper-limb performance.

Overview

The Triceps Brachii makes up nearly two-thirds of upper arm mass, serving as the prime mover for elbow extension and an important secondary stabilizer of the glenohumeral joint.
It’s composed of three distinct heads — long, lateral, and medial — each contributing to different aspects of upper-limb control and power.

Clinically, it’s essential in pushing mechanics, deceleration during pulling, and shoulder stabilization — especially through the long head, which crosses both joints.

Origin & Insertion

  • Long Head: Infraglenoid tubercle of the scapula

  • Lateral Head: Posterior humerus, superior to the radial groove

  • Medial Head: Posterior humerus, inferior to the radial groove

  • Insertion: Olecranon process of the ulna via a common tendon

The long head is the only one that crosses the shoulder, giving it unique roles in both shoulder extension and humeral head stabilization.
That’s also why long head tightness can restrict overhead mobility and affect scapulohumeral rhythm.

Function

  • Primary: Elbow extension (all heads)

  • Secondary: Shoulder extension and adduction (long head)

  • Stabilization: Maintains elbow joint stability during load-bearing

EMG analyses show that the lateral head dominates during high-force tasks, while the medial head handles low-load endurance activity — the long head adds torque when shoulder extension is involved (Escamilla et al., 2023).

Innervation & Blood Supply

  • Innervation: Radial nerve (C6–C8)

  • Blood Supply: Deep brachial artery

Clinical & Training Insights

  • The long head assists in shoulder stabilization and eccentric control in overhead movements — a hidden key in rotator cuff synergy.

  • The lateral head is your strength & hypertrophy driver; it responds best to heavy, compound loading.

  • The medial head fires continuously — even during light activity — maintaining elbow position under load.

  • Triceps tendinopathy is common near the olecranon insertion, especially in lifters who lock out under high load (pressing, dips).

Clinical note: Strength imbalance between the long and lateral heads may contribute to shoulder impingement or posterior capsule stress in pressing athletes (Meyer et al., 2022).

Clinical Relevance

The Triceps isn’t just about extension — it’s about control.
It balances the biceps and brachialis during push–pull cycles, stabilizes the humerus during reaching, and supports scapular mechanics through tension balance.
For lifters, it’s the lockout muscle; for clinicians, it’s a keystone for upper-limb kinetic chain stability.

Take the Next Step

You’ve got the anatomy down — now put it into motion.
If you’re a clinician, let’s talk triceps tendinopathy, shoulder stability, and elbow control.
If you’re an athlete or lifter, let’s talk triceps development and pressing performance.
And if you’re working through elbow pain or push-day limitations — this is where anatomy meets recovery.

𖤓 Watch more breakdowns on YouTube: Treadwell, DPT – Muscle by Muscle Series
𖤓 Book a Virtual Consultation: TreadwellDPT.com/appointments
𖤓 Download free PT tools & anatomy resources: TreadwellDPT.com/resources

Much more in store; even more to come.
Stay tuned, stay locked. Treadwell, DPT. 🚀

Austin Treadwell
Next

Semitendinosus – Anatomy Breakdown