The triceps surae consists of two muscles located at the

calf Calf most often refers to: * Calf (animal), the young of domestic cattle. * Calf (leg), in humans (and other primates), the back portion of the lower leg Calf or calves may also refer to: Biology and animal byproducts * Veal, meat from calves * ...

– 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 The Achilles tendon or heel cord, also known as the calcaneal tendon, is a tendon at the back of the lower leg, and is the thickest in the human body. It serves to attach the plantaris, gastrocnemius (calf) and soleus muscles to the calcaneus ( ...

, 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 The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

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 Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

(sagittal plane) and stabilization of the ankle complex in the

transverse plane The transverse plane (also known as the horizontal plane, axial plane and transaxial plane) is an anatomical plane that divides the body into superior and inferior sections. It is perpendicular to the coronal and sagittal planes. List of c ...

. 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 In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acc ...

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".