The Gastrocnemius, commonly referred to as the “calf,” is located on the posterior compartment of the lower leg. The two-headed muscle is made up of the Lateral Head and the Medial Head. While the two heads of the Gastrocnemius muscle originate on oposite sides of the femoral condyle, they both converge with the fibers of the Soleus to form the Calcaneal Tendon. This tendon travels inferiorly toward the heel of the foot and inserts on the posterior surface of the Calcaneus. Because of these attachment sites, direction of the fibers, and the joints involved, the Gastrocnemius is responsible for knee flexion and plantar flexion.
Superficial part of posterior compartment of the lower leg .
Lateral Head - Lateral condyle and lateral supracondylar line of femur.
Medial Head - Medial condyle and popliteal surface of femur.
Posterior surface of calcaneus via calcaneal tendon.
Plantarflexion of the foot
SHORT AND LONG POSITION
When targeting the short and long position for the Gastrocnemius, we must take into consideration both functions of the Gastrocnemius. Therefore, in order to get the Gastrocnemius in the long position, knee extension and dorsiflexion of the foot is required. The opposite is true for the short position of the Gastrocnemius. Knee flexion and plantar flexion is required.
Tibialis Anterior: While the Tibialis Anterior does not produce knee extension (opposite to the Gastroc's knee flexion), the Tibialis Anterior is thought of as the principal antagonist for the Gastrocnemius because of its powerful ability to produce dorsiflexion.
Gastrocnemius = Tibialis Anterior