The shape of a well-sculpted calf is the envy of every non-runner. That toned muscle group of the lower leg is evidence of many miles of sweat and determination. The amazing calf and Achilles tendon design are part of what allows us to be capable of running at speed and for long distance.

The Power

Anatomically speaking the calf has two layers. The most superficial layer consists of the gastrocnemius muscle combined with the underlying soleus and plantaris. The gastrocnemius is the two headed muscle belly that is so obvious in the runner’s lower leg. It creates the powerful push off of the foot during gait. Directly beneath is soleus, a wider, flatter muscle more associated with stabilizing the body on top of the foot. Plantaris is a smaller muscle sandwiched in between. All three muscles blend into the Achilles tendon, the strongest tendon in the human body. The unique spiral fibre design of the Achilles tendon creates the ability for the tendon to elongate as well as recoil thus storing energy and then releasing it as part of propulsion with running. Running on the midfoot or forefoot as opposed to a heavy heel strike allows maximal benefit of using this potential energy.


The deeper of the two layers is comprised of four muscles. Popliteus is a small muscle behind the knee joint associated with stabilizing the small rotation that occurs here during knee flexion and extension. It can get shortened with overuse and thus contribute to knee pain in the runner. Flexor hallucis longus and flexor digitorum longus start up in the calf region and travel into the foot on the inside. They help stabilize the foot by keeping the toes on the ground and are used during the push off phase in gait. Tibialis posterior also travels from the lower leg and attaches on the inside of the ankle. It activates to control amounts of rolling side to side in the foot (pronation) and assists with balance.

Relationship to Injury

Around 40% of running related injuries occur below the knee. In most overuse injuries such as Achilles tendonitis, plantar fasciitis, calf strain and shin splints (medial tibial stress syndrome) the calf muscles are almost always implicated. Generally a combination of weak and tight muscles combined with overtraining can account for many of these painful and debilitating conditions. Because the calf muscles are so important for creating power, controlling pronation and stabilizing the foot, failure in their function will so often lead to soft tissue breakdown. Be aware that effort induced thrombosis (blood clotting) has been found in the calf region of runners. This presents as calf pain, swelling and discolouration of the lower leg and needs to be treated medically.

Injury Prevention

As the minimalist shoe trend (use of shoes with less cushioning and support) gains popularity our calf muscles will be called into greater action. There is evidence that barefoot running activates the calf muscle differently as the foot and leg muscles become the shock absorbers as opposed to relying on the shoe. Utilizing small amounts of barefoot running can help strengthen this powerful area and provide injury prevention for the runner. Regular heel lifting exercises will also help with tuning up these muscles. Don’t forget to stretch the calf regularly as it will get tight with increased training volume and intensity. Adhesions in the muscle can build up to a point of sudden calf strain or tear during a run. Both massage and stretching can help prevent this.

Nurture this beautiful muscle group. Keep those non-runners envious!


(Originally published in the Calgary Marathon Race Guide 2010)