Triceps Brachi

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Muscles that move the humerus¹

Figure 2: Muscles that move the Forearm¹

Figure 3: Left Scapula (Lateral view)²

Figure 4: Left Humerus (Posterior view)²

Reading list

• Triceps and Anconeus Muscle³
• ⁴
• Long head MMT⁵
• Middle head MMT⁵
• Lateral head MMT⁵

Muscle	Origin	Insertion	Innervation	Action
Triceps brachii lateral head	Posterior humerus just *proximal* to radial groove Lateral intermuscular septum	Olecranon of Ulna	Radial n. C6 - C8	Elbow: Extension
Triceps brachii Long head	Infraglenoid tubercle of Scapula	Olecranon of Ulna	Radial n. C6 - C8	Elbow: Extension GHJ: Extension, Adduction
Triceps brachii medial head	Posterior humerus just distal to radial groove Medial intermuscular septum	Olecranon of Ulna	Radial n. C6 - C8	Elbow: Extension

Long Head

Origin

The triceps long head as a proximal origin on the Infraglenoid tubercle of scapula⁶.

There is also attachments to the glenohumeral capsule.

Figure 5: Left Scapula (Anterior view)²

Insertion

Olecranon process of Ulna⁶

Innervation

Radial N. (C6, C7, C8)⁶

Action

• Elbow: Extension⁶
• Shoulder: Extension, Assists in Adduction⁶

When looking at the long head’s origin and insertion, it is lengthened by shoulder flexion, as a result it optimizes the length-tension curve⁷. The Long head can produce the most force when the shoulder is flexed⁷.

Adductor force couple

The triceps brachii long head and latissimus dorsi form a “force adductor couple”⁷. The adduction and extension moment created by the latissimus dorsi results in inferior displacement of the humeral head, the triceps long head contracts and its abductive component counteracts the latissimus dorsi creating a superior glide⁷. This results in no net vertical translation of the humeral head and keeping its optimal position in the glenoid.

Thus although the triceps long head has an “abductive” component, we consider it to function as an “adductive assist.”

Medial Head

Origin

• Posterior surface of humerus (distal to radial groove)⁶
• Medial intermuscular septum⁶

Insertion

Olecranon process⁶

Innervation

Radial N. (C6, C7, C8)⁶

Action

Elbow: Extension⁶

Lateral Head

Origin

• Posterior surface of humerus (prox to radial groove)⁶
• Lateral intermuscular septum⁶

Insertion

Olecranon process⁶

Innervation

Radial N. (C6, C7, C8)⁶

Action

Elbow: Extension⁶

Notes

Triceps Reflex

Triceps reflex can be used to assess C7 nerve root⁸

References

1.

Betts JG, Blaker W. Anatomy and Physiology. 2nd ed. OpenStax; 2022. https://openstax.org/details/books/anatomy-and-physiology-2e/?Book%20details

2.

Gray H. Anatomy of the Human Body. 20th ed. (Lewis WH, ed.). Lea & Febiger; 1918. https://www.bartleby.com/107/

3.

Donnelly JM, Simons DG, eds. Travell, Simons & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Third edition. Wolters Kluwer Health; 2019.

4.

Neumann DA, Kelly ER, Kiefer CL, Martens K, Grosz CM. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed. Elsevier; 2017.

5.

Weinstock D. NeuroKinetic Therapy: An Innovative Approach to Manual Muscle Testing. North Atlantic Books; 2010.

6.

Gilroy AM, MacPherson BR, Wikenheiser JC, Voll MM, Wesker K, Schünke M, eds. Atlas of Anatomy. 4th ed. Thieme; 2020.

7.

Jones B. B Project Foundations. b Project; 2025.

8.

Hong CG, Nam WD. Reliability and Diagnostic Accuracy of Standard Dermatomes and Myotomes for Determining the Pathologic Level in Surgically Verified Patients With Cervical Radiculopathy. Neurospine. 2022;19(4):1006-1012. doi:10.14245/ns.2244194.097