Your calf muscles are part of the posterior fascia line (hamstrings, buttocks, back) that help produce power and speed in sprinting and jumping. They are made up of two primary muscles: gastronemius (superficial layer) and soleus (deep layer). The calcaneal tendon (Achilles tendon) shares a similar nerve and blood supply as the superficial muscles and is the thickest and strongest tendon in the body.
The gastrocnemius muscle has two heads that attach from the lateral and medial condyles of the femur and the knee capsule to the calcaneus (heel bone) by way of the calcaneal tendon. The soleus muscle lies underneath the gastrocnemius and also attaches from the head of the fibula and the inner border of the tibia to the calcaneus. The calcaneal tendon's attachment begins near the middle of the calf, meeting the muscle fibers of the gastrocnemius, and inserts into the calcaneus near the bottom.
The gastrocnemius and the soleus form a group called the triceps surae, which refers to the calf muscle group. They share the tibial nerve, which is a branch of the sciatic nerve.
The calf muscles function primarily as a plantarflexor of the footm where they contract when the foot is pointing down. Along with the hamstrings, quadriceps, and hip muscles, they function both as accelerators and decelerators during explosive movements like sprinting, leaping, and jumping.
The calcaneal tendon is pulled when the calf muscles are contracted, which pushes the foot downward and enables you to walk, run, and jump. Each tendon may bear between three and 12 times a person’s body weight during a sprint or pushoff, depending on stride, speed, terrain, and additional weight being carried or pushed.
Tennis leg is a condition where the gastrocnemius muscle is ruptured from straining of the muscle. This is caused by eccentric loading of the ankle while the knee is extended or by a sudden, forceful plantarflexion of the ankle, such as vertical jumping, side leaping, and starting a sprint.
Achilles tendonitis is an inflammatory condition that is caused by repetitive stress and strain upon the calcaneal tendon. This often accompanies calf tightness, hamstring strain, and plantar fasciitis.
Injuries to the calves and tendons can be prevented by a combination of strength conditioning and mobility training. In conditioning, the calves must be moved in their full range of motion to give them more elasticity and to improve strength integrity in the tendon and ligaments of the foot.
Recovery is often overlooked as part of the training. Give your body time to heal by avoiding high-intensity and high-stress exercises for one or two days (depending on your physical fitness), stretching the calves, thighs, and hips. Getting a massage can help speed recovery.
Remember that your calves are part of a network of connective tissues (kinetic chain) that are dependent on one another. When training your calves, do not isolate them by doing "calf exercises." Instead, work on your entire body by doing exercises that emphasize body acceleration and deceleration, weightbearing on the lower body, and stepping and turning in different directions.
Sample exercises include squats, multiplanar lunges, jumping rope, sprinting, and rotation exercises with a resistance band, pulley, or medicine ball.