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Triceps brachii muscle: Origin, insertion, innervation, and function

Your complete evidence-based guide to the anatomy of the triceps brachii muscle.
Headshot of the Critical Body Personal Trainer Liam Brown
Written By Liam Brown
Last Updated on 2nd May 2022
The anatomy of the triceps brachii muscle
The triceps, commonly called the triceps brachii, is a three-headed, biarticular muscle that’s located on the posterior compartment of the arm and which extends the elbow joint. It’s made up of a medial, lateral, and long head, with the former two heads originating at the humerus and the latter arising from the scapula.

Triceps brachii origin and insertion

The triceps brachii long head originates from the infraglenoid tubercle of the scapula, which is the lateral part of the scapula that’s located inferior to the glenoid fossa. [1]

The lateral head, which is widely believed to be the strongest of the three triceps brachii heads, arises from the posterior and lateral surface of the humerus and is superior to the radial groove (also called the radial sulcus). The lateral head of the triceps brachii also has muscle fibers that connect to the intermuscular septum. [2]

The medial head is the smallest head of the triceps and, like the lateral lead, originates on the posterior surface of the humerus. It also connects to the lateral and medial intermuscular septum. Unlike the lateral head, however, the medial head of the triceps brachii is inferior to the radial groove.

The three heads of the triceps brachii converge at a common tendon, which inserts into the olecranon process of the proximal ulna and blends with the forearm fascia. (physiopedia)

Triceps brachii innervation

The triceps brachii is innervated by the radial nerve (C6 innervates the lateral head, C7 innervates the long head, and C8 innervates the medial head). [3] The radial nerve is the nerve that arises from the posterior cord of the brachial plexus, which is a network of nerves that supplies the shoulders, arms, and hands.

Research from the esteemed Surgical and Radiologic Anatomy journal also shows that in some cases, the long head is innervated by the axillary nerve. [4]

Similarly, a 2008 study from the Clinical Orthopaedics and Related Research journal demonstrates that the medial head of the triceps brachii is sometimes innervated by the ulnar nerve due to its insertion at the olecranon process near the forearm. [5]

Triceps brachii blood supply

The triceps brachii gets its blood supply from the deep brachial artery, which is a blood vessel that originates from the posterior and lateral sides of the brachial artery.

The long head also gets its arterial supply from the posterior humeral circumflex artery, which arises from the third part of the axillary artery.

Triceps brachii function and action

A man demonstrating the primary triceps brachii function; elbow extension
The primary triceps brachii function is elbow extension, which is to say straightening the arm. The medial head is always active during elbow extension, whereas the lateral and long heads only become active when the triceps are required to push against resistance.

Due to being the strongest head, the lateral head of the triceps brachii consists of mainly fast-twitch type IIb muscle fibers that enable it to contract forcefully under resistance. [6]

On the contrary, the medial head is a slow-twitch dominant muscle that consists of predominantly type I fibers.

Only the long head crosses the shoulder joint and attaches to the scapula. As such, the long head assists with shoulder extension, shoulder adduction and also helps to keep the glenohumeral joint stable by holding the head of the humerus in the glenoid cavity, thus preventing displacement of the humerus.

The biceps brachii is the triceps brachii antagonist; when the triceps contract, the biceps relax.

References

  1. AnatomyZone. (2020, March 25). Triceps | Muscle Anatomy [Video]. YouTube. https://www.youtube.com/watch?v=YxlfXFLmZ3M

  2. Wikipedia contributors. (2021). Triceps. Wikipedia. https://en.wikipedia.org/wiki/Triceps

  3. Sendic, G. (2021, August 18). Triceps brachii muscle. Kenhub. https://www.kenhub.com/en/library/anatomy/triceps-brachii-muscle

  4. de Sèze, M. P., Rezzouk, J., de Sèze, M., Uzel, M., Lavignolle, B., Midy, D., & Durandeau, A. (2004). Does the motor branch of the long head of the triceps brachii arise from the radial nerve? Surgical and Radiologic Anatomy, 26(6), 459–461. https://doi.org/10.1007/s00276-004-0253-z

  5. Bekler, H., Wolfe, V. M., & Rosenwasser, M. P. (2009). A Cadaveric Study of Ulnar Nerve Innervation of the Medial Head of Triceps Brachii. Clinical Orthopaedics & Related Research, 467(1), 235–238. https://doi.org/10.1007/s11999-008-0535-6

  6. Lucas-Osma, A. M., & Collazos-Castro, J. E. (2009). Compartmentalization in the triceps brachii motoneuron nucleus and its relation to muscle architecture. The Journal of Comparative Neurology, 516(3), 226–239. https://doi.org/10.1002/cne.22123

Workouts

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A man performing a bodybuilding chest shoulder tricep workoutChest shoulders and triceps workout routine

Tricep FAQs and More

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A man doing a dips vs diamond push ups comparisonDiamond pushups vs dips for triceps mass
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Skull Crushers

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A man doing skull crushers with a plateHow to do plate skull crushers for your triceps
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A man doing Smith machine skull crushers for his tricepsHow safe and effective are Smith machine skull crushers?
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A man doing TRX skull crushers for his tricepsHow to do TRX skull crushers for your triceps
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A man doing dumbbell skull crushers on the floorFloor skull crushers tutorial and variations
A man performing decline EZ bar skull crushersHow to do decline skull crushers with a barbell and dumbbells
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A man doing a pronated skullcrusher with dumbbellsThe complete guide to pronated skull crushers
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A man performing a good skullcrusher alternativeThe best skullcrusher alternative for triceps development revealed
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Tricep Extensions

A man performing a standing dumbbell overhead tricep extension exerciseHow to do a standing dumbbell overhead tricep extension
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A man doing a seated barbell overhead tricep extensionHow to do an overhead seated barbell extension
A man doing an overhead rope tricep extension at the gym using cablesHow to do a rope overhead cable extension
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A man doing a one arm overhead cable tricep extension with a single ropeHow to do a one arm overhead cable tricep extension
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A man performing a cable cross triceps extension at the gymHow to do a cable cross tricep extension correctly
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A man performing a cable horizontal tricep extension at the gymHow to do a cable horizontal tricep extension
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A man performing a bent over tricep extension during his workoutHow to do a bent over tricep extension for your arms
A man doing front to back tricep extensionsHow to do front to back tricep extensions
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A man performing a dumbbell tricep extension lungeHow to do a tricep extension with a lunge (static, lateral, reverse)
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A man performing a plank to triceps extensionHow to perform a plank to triceps extension
ring tricep extensionHow to do ring tricep extensions
A man doing a standing overhead plate tricep extensionHow to do every variation of the plate tricep extension
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A man with a painful shoulder due to overhead tricep extensionsTricep Extension Shoulder Pain

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A man doing wall tricep extensionsHow to do wall tricep extensions for the best results
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A man performing an EZ bar lying tricep extension on a flat benchHow to do a flat bench EZ bar lying tricep extension
A man doing a lying barbell tricep extensionBarbell lying tricep extension pros, cons, and variations
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A man doing a decline barbell triceps extensionHow to do a decline barbell extension for your triceps
A man doing a decline cable tricep extensionDecline cable tricep extension tutorial and variations
A man doing a decline dumbbell triceps extensionHow to do a decline dumbbell triceps extension
A man doing a decline EZ bar triceps extensionDecline EZ bar triceps extension tutorial
A man doing an incline dumbbell tricep extensionIncline dumbbell tricep extension variations and comparison
A man performing an incline barbell triceps extensionIncline barbell triceps extension pros and cons
A man performing an incline EZ bar triceps extensionIncline EZ bar tricep extension tutorial and training recommendations
A man performing a lying cable tricep extensionHow to do a cable lying tricep extension with every attachment
A man doing a dumbbell floor tricep extensionFloor tricep extension tutorial, advantages, and variations
A man doing an alternating dumbbell lying triceps extensionHow to do an alternating dumbbell lying triceps extension
A man doing a single arm lying triceps extensionHow to do a single arm lying tricep extension with one dumbbell
A man performing a pronated tricep extensionHow to perform a pronated tricep extension
A man doing some dumbbell rolling triceps extensionsRolling dumbbell tricep extension mistakes and benefits
A man performing a dumbbell side leaning tricep extension on a matHow to do a side leaning tricep extension
A man doing a dumbbell stability ball tricep extensionHow to do a stability ball lying triceps extension with dumbbells
A man doing a tricep extension with a TRXTRX tricep extension and press tutorial and variations
A man performing standing kettlebell tricep extensionsHow to do a lying and overhead kettlebell tricep extension
A man doing resistance band overhead tricep extensionsHow to do every resistance band tricep extension variation
A man doing a barbell French press workout for his tricepsHow to do the standing barbell French press exercise
A man doing a dumbbell French press for his tricepsHow to do a standing and seated dumbbell French press
A man doing a standing EZ bar French press for his tricepsHow to do a standing, lying, and seated EZ bar French press
A man at the gym doing a rope cable French press for his tricepsHow to do every type of cable French press
A man doing an incline French press with an EZ bar for his tricepsHow to do an incline French press with an EZ bar and dumbbells
A man doing a decline bench French pressHow to do a decline French press
A man doing a standing kettlebell French press during his strength training workoutHow to perform a kettlebell French press
A man doing a resistance band French press for his tricepsHow to do every type of resistance band French press
A man doing a standing medicine ball French press for his tricepsHow to perform a medicine ball French press
A man doing a tall kneeling French press with a dumbbellHow to do a kneeling French press
A man performing a French press on a stability ball with a dumbbellHow to perform a French press on a stability ball
A man performing a deadstop French press for his tricepsHow to do a deadstop French press
A man doing a single arm dumbbell French press for his tricepsHow to do a standing and seated dumbbell single arm French press
A man doing a seated barbell French press for his tricepsHow to do a seated French press with a barbell

Pushdowns

A man doing a standing cable tricep pushdown exercise with a rope attachment during his workoutHow to do a cable tricep pushdown with a rope
A man doing straight bar pushdowns for his tricepsHow to do a straight bar cable pushdown for your triceps
A man doing a tricep v bar pushdownHow to do a cable v bar pushdown for your triceps
A man performing a reverse grip tricep pushdown extensionHow to do a reverse grip cable pushdown (underhand pressdowns)
A man performing a one arm reverse grip tricep extension with a single handleHow to do a one arm reverse grip tricep extension (pushdown)
A man doing a one arm tricep pushdown with a single cable handleHow to do a cable one arm triceps extension (single arm pushdown)
A man performing a tricep EZ bar push downHow to perform a cable EZ bar tricep pushdown
A man performing a close grip push down for his tricepsHow to perform a close grip tricep pushdown
A man doing a wide grip tricep pushdownHow to do a wide grip cable tricep pushdown
A man doing a banded tricep pushdown exercise during his workoutHow to do every type of resistance band tricep pushdown
A man doing kneeling tricep pushdownsHow to do a kneeling tricep pushdown with every attachment
A man performing an isometric tricep pushdownHow to perform an isometric triceps pushdown
A man doing a Swiss ball tricep pressdownHow to perform a stability ball tricep pushdown
A man performing a rocking tricep pushdownHow to perform a rocking tricep pushdown
A man doing a tricep drag pushdownHow to perform a tricep drag pushdown
A man doing a seated tricep pushdownHow to do a seated tricep pushdown and an incline tricep pushdown
A man performing a tricep pushdown on an assisted pull up machineHow to perform a tricep pushdown on an assisted pull-up machine
A man demonstrating a good rope tricep pushdown alternativeThe best tricep pushdown alternative that you can do at home with dumbbells
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