The triceps surae consists of two muscles located at the calf – the two-headed

gastrocnemius The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtalar ...

and the

soleus In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg (the calf). It runs from just below the knee to the heel, and is involved in standing and walking. It is closely connected to the gastrocnemius mu ...

. These muscles both insert into the calcaneus, the bone of the heel of the human foot, and form the major part of the muscle of the posterior leg, commonly known as the calf muscle.

Structure

The triceps surae is connected to the foot through the Achilles tendon, and has 3 heads deriving from the 2 major masses of muscle. * The superficial portion (the gastrocnemius) gives off 2 heads attaching to the base of the femur directly above the knee. * The deep (profundus) mass of muscle (the soleus) forms the remaining head which attaches to the superior posterior area of the tibia. The triceps surae is innervated by the

tibial nerve The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus. Structure Popliteal fossa The tibial nerve is the larger terminal branch of the sciatic nerve with root val ...

, specifically, nerve roots L5–S2.

Function

Contraction of the triceps surae induce plantar flexion (sagittal plane) and stabilization of the ankle complex in the transverse plane. Functional activities include primarily movement in the

sagittal plane The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and div ...

, stabilization during locomotion (walking, running), restraining the body from falling and power

jumping Jumping or leaping is a form of locomotion or movement in which an organism or non-living (e.g., robotics, robotic) mechanical system propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, gallo ...

. By controlling the disequilibrium torque, the triceps surae can affect force through the exchange of potential into kinetic energy.

Clinical significance

Calf strain (torn calf muscle)

A calf

strain Strain may refer to: Science and technology * Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes * Strain (chemistry), a chemical stress of a molecule * Strain (injury), an injury to a mu ...

refers to damage to a muscle or its attaching tendons. A premature return before recovery is achieved will result in a prolonged recovery or incomplete return to baseline prior to injury. Stretches such as alternating calf raises can improve

flexibility Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a bo ...

as well as mobilize legs before running. Calf muscles are a common place for fasciculations.

Additional images

File:Triceps surae - animation.gif, Animation. Gastrocnemius and Soleus are shown in different colors. File:Sobo 1909 303.png, Illustration of the

. File:Sobo 1909 304.png, Illustration of

. File:Sobo 1909 579-580.png, Nerves, arteries and veins surround the gastrocnemius and soleus. File:Braus 1921 293.png, Cross section of the lower leg, with triceps surae at back (soleus and gastrocnemius) File:Sobo_1909_720.png, Nerves and blood-vessels overlying the triceps surae File:Medial view of a cadaver dissection of the gastrocnemius–soleus junction - with text.png, Photograph of the

junction.

Etymology and pronunciation

The term is pronounced . It is from Latin ''caput'' and ''sura'' meaning "three-headed uscleof the calf".