The Anatomy of the Triceps

The triceps muscle is a main muscle of the upper arm, running from the top of the shoulder to the elbow at the back of the arm. When the triceps muscle contracts (shortens or tightens), it causes the elbow to straighten.

This article will describe the anatomy, location, and function of the triceps and associated conditions.

Anatomy

The triceps, or triceps brachii, is the large muscle found at the back of the arm. As are other muscles of the arms and legs, the triceps muscle is a voluntary muscle, meaning it's a muscle you choose to move. Triceps are made up of skeletal muscle fibers that contract under conscious control. The triceps is a fusiform, or spindle-shaped, muscle that is wider in the middle and narrower at each end.

"Triceps" means “three heads,” which refers to the subdivision of the triceps muscle into three different segments called heads. These include the:

• Long head: Running from the shoulder blade down along the length of the humerus (upper arm bone)
• Lateral head: Located on the outer side of the back of the arm
• Medial head: Located on the inner side of the back of the arm

All skeletal muscles connect to bones via tendons. Each head of the triceps has a separate short tendon that attaches the muscle heads to the shoulder blade and arm bones where they originate. All three heads merge together and form one thicker and longer tendon that attaches the entire muscle to the elbow. 

Location 

The triceps is located at the back of the upper arm and covers the majority of the backside of the humerus (upper arm bone). Each of the three heads of the triceps originates at a different location. 

The long head originates at the infraglenoid tubercle, a ridge along the outermost portion of the shoulder blade that connects with the humerus to form the shoulder joint. The medial head and lateral head start at the medial (inner) and lateral (outer) sides of the upper portion of the humerus.

All three muscle heads of the triceps run down the back of the arm and join close to the elbow to form one common tendon. This triceps tendon attaches to the olecranon process, the pointy projection at the end of the ulna bone of the forearm that forms the elbow.

Function

The main function of the triceps is to extend the forearm at the elbow joint to straighten the elbow. Extension, or straightening, of the elbow is a necessary everyday movement needed for reaching, getting dressed, and pushing off from armrests to stand up from a chair. 

Because the long head of the triceps also travels across the shoulder joint, it helps extend the arm back behind the body at the shoulder joint. Contraction of all of the muscle heads of the triceps is controlled by the radial nerve.

The triceps is also one of few muscles that demonstrates a distinct reflex. When the triceps tendon is sharply hit near the elbow when the arm is lifted up to shoulder height with the elbow bent, the forearm will involuntarily extend. Presence of this reflex indicates normal functioning of the C7 spinal nerve root.

Associated Conditions

The most common condition affecting the triceps is triceps tendonitis, which is inflammation of the triceps tendon from repeated overuse. Without adequate rest from repeated activities that involve extending the elbow, the triceps tendon becomes irritated and inflamed, resulting in pain, tenderness, swelling, and muscle weakness in the triceps.

Triceps tendonitis frequently occurs in people who participate in sports like baseball and tennis, or in people who lift weights, which requires repeated pushing and pressing movements of the arms. 

Additionally, the triceps muscle or tendon can become strained or sprained through forcibly extending the elbow. This can occur through quick overhead movements or in positions that involve bearing weight through the arms, such as when performing a push-up or handstand. 

While rare, a tear in the triceps can occur. This can happen from heavy weight lifting or from falling on an outstretched arm. Use of performance-enhancing anabolic steroids or health conditions like rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and diabetes may also increase the risk of tendon tearing.

Rehabilitation

Rehabilitation for triceps injuries initially involves rest, ice, and pain-relieving medications, if needed. Gentle stretching of the triceps by bending the elbow can help maintain its full range of motion while strengthening exercises will help build up the muscle fibers after injury. 

At first, light or no resistance will be used in order to help improve contraction of the triceps muscle without causing further pain or injury. As the triceps builds up more strength, more resistance and more challenging exercises can be added until you have full use of your arms for everyday activities and sports and exercises. 

For triceps tendonitis, eccentric exercises, which are exercises that involve slow and controlled relaxation of muscle contraction against resistance, can help improve the strength of your triceps tendon to withstand heavy loads. 

For triceps ruptures, or tearing of the triceps tendon from the humerus bone, wearing an elbow brace will help control the range of motion of your elbow to protect your triceps as it heals and to prevent further injury. In severe cases of triceps ruptures, surgery may be needed to reattach the torn triceps tendon, followed by several weeks of physical therapy to strengthen the triceps muscle.

Summary

The triceps are the large muscles that encompass most of the back of the upper arm. The triceps has three different heads, or muscle segments, that all attach to the elbow. These include the medial, lateral, and long heads.

When contracted, all heads of the triceps extend, or straighten, the elbow, while the long head assists with extending the arm back behind the body at the shoulder joint. Triceps tendonitis, or inflammation of the triceps tendon, is the most common condition affecting the triceps. It can be treated with ice, rest, and physical therapy that uses stretching and strengthening exercises.