The Heart of the Calf

I am continually amazed at the brilliance of evolution and the human form. The more I learn about the body in motion the more dumbfounded I become with awe. For instance, while attending a recent course of “Anatomy in Motion” one of the teachers mentioned, in passing, how the calf muscles are the heart of the lower body. This hit me like a bus. I never stopped to consider this until now. If you do not yet understand the significance of this simple statement, let me explain.

From the moment our ancestors changed from quadrupeds to bipeds, everything began to change. One of the biggest changes was how gravity would affect the upright body. The spine would develop an s-curve. The hand-like structure of what would become the foot would see the thumb shift into the big toe. The shape and position of the pelvis would change. The legs would become longer and larger than the arms. Eventually, with the use of fire to break down our food through cooking, humans would spend less time eating and have more time to explore their surroundings. The rest we will save for the anthropologists. However, the one thing that stays in my mind is how the body became dependent on this “new” upright movement to maintain organic function.

Our bodies are continually pulled toward the center of the planet by gravity. Our fluids are pulled toward our feet and need a pumping mechanism to bring the fluid upward. Traditionally we have viewed the heart as the main source for circulation in the body but think of its position in the body. It is not at the lowest point as you normally would find a pump in a fountain. Instead, the heart is positioned close to the brain where blood supply is the most critical for survival. If the heart was the only source to pump fluid up from the toes, imagine how much strain it would undergo. It must have help to achieve the circulation needed; enter the calf muscles.

The calf muscles are made up of two groups: the gastrocnemius and the soleus. Both groups of muscles attach to the Achilles tendon while the other ends connect to either the shin bone (tibia and fibula) or thigh bone (femur). The Achilles tendon attaches to the heel bone (calcaneus) which moves in many directions when we walk. As we walk the ankle flexes, extends, rotates, inverts and everts. Meanwhile, the bones of the lower leg and thigh flex and extend, rotate, adduct and abduct. This means that the calf muscles are constantly being stretched and shortened in all sorts of direction, almost like an accordion. This muscular action invites blood in and the squeezes it out…just like the heart. The calf is the local pumping station of the legs! Ask any person who cannot use their legs if they have swelling in their feet and legs. Their answer will almost always be yes. Their heart is still pumping but what’s missing is their ability to walk.

So is the heart part of the muscular system or the cardiovascular system? Is our calf muscles part of our muscular system or our cardiovascular system?

I could go off on this subject all day, but I think you see the point. In anatomy classes, we learned that the body is comprised of systems: the pulmonary system, endocrine system, cardiovascular system, nervous system, skeletal system, muscular system, etc. Although we understood these systems were interdependent, we nevertheless compartmentalized each system. In breaking down the body, we lost our appreciation that there is only one system, the human system. Movement is the key to keeping all systems operating. So get up and go for a walk. Your overworked heart will be happier when it gets help from your calves.

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