The two main muscles of the posterior lower leg, or the calf, are the gastrocnemius and the soleus. The gastrocnemius is the largest (forming the bulge visible beneath the skin) and most visible (superficial) of the two muscles comprising the calf in the back of the lower leg. The soleus muscle lies deep underneath the gastrocnemius, and therefore, is not so prominent. We can rightly say that the gastrocnemius muscle is the one that is responsible for the vast majority of the visual impact of the calf. You have two gastrocs, one in each lower leg.
Very often in anatomy you’ll hear the term “triceps surae“, meaning “three-headed muscle of the calf“. The origin for this fancy term is quite simple. The triceps surae is made of the two head (lateral and medial) of the gastrocnemius muscle and of the soleus muscle. Because these two muscles share the same insertion (via the Achilles tendon) and perform the same function they are collectively known as the “triceps surae“.
Muscle location, size, appearance
The gastrocnemius, or gastroc, is the diamond-shaped muscle (like an upside-down heart) located at the back of the lower leg, directly under the skin. It is the largest calf muscle that lies on top of the smaller soleus muscle. It has a medial head and a lateral head. In fact, these two parts or “heads” together create its diamond shape. The gastroc allows you to rise up on your tiptoes to see over your neighbor’s fence. Check out the calves of any competitive bicyclist, and you’ll see precisely what this muscle looks like. Because of its heart-shaped appearance it’s also highly desired by bodybuilders. The plantaris muscle and a portion of its tendon run between the two muscles.
The function of the gastrocnemius muscle
The primary function of the gastrocnemius is to flex the foot at the ankle and raise you onto your toes when your legs are straight. The soleus also flexes the foot at the ankle joint, but plays a bigger role when the knees are bent.
- flexing the foot at the ankle joint;
- flexing the leg at the knee joint;
The gastrocnemius is crucial for running, jumping and other fast & explosive movements of leg, and to a lesser degree for walking and standing. This is explained in more detail later in the article.
Gastrocnemius muscle origin, insertion, and innervation
The gastrocnemius originates on the lateral and medial condyle of the femur and inserts on the posterior side of the calcaneus via the Achilles tendon. In other words, the tendons of gastrocnemius and soleus fuse to form the Achilles tendon, which passes behind the ankle joint and attaches to the calcaneus (heel bone).
The gastrocnemius muscle is innervated by a nerve we call the tibial nerve. It arises from the large sciatic nerve. The tibial portion is mainly served by the first and second sacral nerves from your lower back.
In short:
- Origin: medial head – medial condyle of femur (posterior surface); lateral head – lateral condyle of femur (posterior surface);
- Insertion: calcaneus (via calcaneal or Achilles tendon)
- Innervation: tibial nerve (S1, S2)
The most significant differences between the gastrocnemius and soleus muscle
Other than size and appearance (large vs. small; heart- or diamond-shaped vs. broad & flat), there is a great difference between the gastrocnemius and the soleus. Only the gastrocnemius is a multijoint muscle, crossing your knee and your ankle. This particularity will have serious repercussions for every calf exercise. Because it is a single-joint muscle, the soleus participates in all calf exercises whether or not the leg is bent. However, the more you bend your leg, the less the gastrocnemius will be able to assist with that movement. This is why exercises in which you bend your leg at 90 degrees will isolate the soleus and neglect the gastrocnemius.
Last but not least, the gastrocnemius muscle contains white (Type II or fast twitch muscle fibers) in contrast to the soleus muscle, which contains red (type I or slow twitch) muscle fibers. Muscle fibers present in the gastrocnemius muscle (type II) forcefully contract to produce explosive movements, but experience fast fatigue. These fibers are crucial for heavy weight training and sprinting. Soleus muscle, on the other hand, primarily consists of slow twitch (Type I) muscle fibers which are highly fatigue resistant. This means that we use them for aerobic and endurance-type activities that range from maintaining posture, walking, jogging, or long-distance running. Therefore, these type of muscle fibers cannot produce the forceful contractions required for creating fast and powerful movements.
Gastrocnemius muscle strengthening exercises
Bent-legged calf work takes the gastrocnemius out of play according to the extent of leg flexion, and focuses the work on the soleus. But bent-legged calf work is less productive than straight-legged work for overall calf growth.
Therefore, the gastrocnemius muscle is targeted when the legs are straight. Exercises like the leg-press calf raise, standing barbell calf raise, and machine standing calf raise are best for targeting this area of the calf.
The soleus, on the other hand, is better targeted with seated calf raises or any calf raise that is performed with the knee bent to about 90 degrees.
It is possible to target the lateral or medial head of the gastrocnemius by varying foot position. An externally rotated position (feet pointed out) activates the more medial (toward center of the body) gastrocnemius. An internally rotated position (feet pointed in) activates the more lateral (toward the outside of the body) gastrocnemius.
The best way for growing big calves is following our calf training tips!
Best stretching technique for the gastrocnemius muscle
- Floor board straight-knee calf stretch
- Lunging straight-knee calf stretch
- Pike straight-knee calf stretch
- Floor-seated straight-knee calf stretch (requires good hip and lower back flexibility)
- Floor-seated straight-knee calf stretch with towel
- Step straight-knee calf stretch
- Wall straight-knee calf raise
Self myofascial release techniques
- Foam roller
- Lacrosse ball. Here’s how you can use a lacrosse ball to release your calves.
- Sprinter stick. Here’s how to use “sprinter stick” to release your calves.
Summary
The bulk of the calf is made up of the gastrocnemius, the large heart- or diamond-shaped muscle at the rear of the lower leg.
