The gastrocnemius is the largest and most superficial muscle of the calf, extending from the posterior knee to the heel. It is one of the three triceps surae (triceps = “three heads” and surae = “calf”) muscles. The plantaris and soleus are also part of this group, which converges into the calcaneal tendon and inserts on the posterior surface of the calcaneus. Compared to the other two muscles, the bulk of the gastrocnemius is more proximal and divided between two large, symmetrical segments or “heads.”
The two heads of gastrocnemius are located medially and laterally, respectively, forming the inferior borders of the popliteal fossa at the knee. Moving inferiorly, they merge near the middle of the calf before descending to the calcaneal tendon. Significant variation occurs in the size and position of the two heads and provides a visual clue as to the genetic predisposition of individuals. Individuals with large gastrocnemius heads and a very short calcaneal tendon tend to have a greater propensity for explosive power. Those with smaller heads and a long calcaneal tendon are more suited to sustained or endurance activities. The structural differences are primarily the result of muscle fiber-type distribution, which is genetically determined (see Massage & Bodywork, “Skeletal Muscle Fiber,” January/February 2017, page 43). Gastrocnemius contains mainly fast-twitch fibers, which are recruited rapidly but fatigue quickly, and is, therefore, more developed in individuals with a higher percentage of this fiber type.
The gastrocnemius crosses both the knee and the ankle, allowing it to perform both knee flexion and ankle plantar flexion. Compared to the hamstring muscles, the gastrocnemius has relatively little mechanical advantage for knee flexion and serves primarily as a plantar flexor of the ankle. It also has minimal ability to stabilize the ankle due to the posterior orientation and narrow attachment of the calcaneal tendon.
The soleus is a synergist to the gastrocnemius for plantar flexion, but which of these two muscles is most active during this movement is mainly driven by the position of the knee: If the knee is extending or extended (as when rising from a squatting or seated position or jumping), the gastrocnemius is more active. If the knee is flexed (as with relaxed walking or static standing), the soleus is more active. With the knee extended, the gastrocnemius is pre-stretched or placed under tension, thus maximizing its contractility and mechanical advantage for pushing off or lifting the ankle up from the ground. With the knee flexed, the gastrocnemius is slacked, reducing its contractility and placing greater emphasis on the soleus for generating plantar flexion.

Palpating the Gastrocnemius

Positioning: client prone.
1. Stand facing the client’s leg and locate the bulk of muscle just distal to the popliteal fossa with your palm.
2. Slide your hand medially and laterally to differentiate the two large heads of the gastrocnemius.
3. Continue to palpate distally as the gastrocnemius converges into the calcaneal tendon.
4. Resist as the client plantar flexes to ensure proper location.

Client Homework: Downward-Facing Dog Pose

1. Begin on all fours with knees hip-width apart, hands about a foot in front of your shoulders, and palms flat.
2. Tuck your toes and lift your hips as you drop your chest back toward your thighs.
3. Keep your knees slightly bent and your wrists and shoulders strong and stable.
4. Keeping your head relaxed, continue lifting your hips up and back as you straighten your knees and drop your heels toward the floor.
Editor’s note: The Client Homework element in Functional Anatomy is intended as a take-home resource for clients experiencing issues with the profiled muscle. The stretches identified in Functional Anatomy should not be performed within massage sessions or progressed by massage therapists, in order to comply with state laws and maintain scope of practice.