Login | July 17, 2025
Our second heart
PETE GLADDEN
Pete’s World
Published: January 29, 2024
How much do you know about the triceps surae?
That’s the scientific name for the calf muscles, the gastrocnemius and soleus.
And though we generally take them for granted they’re absolutely foundational for walking, for posture and for work and sporting activities. They also effect crucial movements of the hip and the lumbar areas.
But there’s one function the calves are responsible for that’s just about as obscure as its scientific name - and that function involves returning blood to the heart.
That’s right, also known as the “second heart,” the calves pump blood out of the legs and back to the heart.
According Dr. Simon Wikler, MD, “The gastrocnemius is anatomically designed to function as a pump when we walk and run which assists the veins to deliver de-oxygenated blood back to the heart to be re-oxygenated.”
As such the calves turn out to be a vital component in keeping the heart healthy.
So let’s take a closer look at this little known but super important function of the calf muscles.
And we’ll begin the discussion with a generalized description of how the circulatory process works.
Just one pump of the heart exerts enough pushing power to deliver oxygen rich blood throughout the body, reaching even the lower extremities in a matter of seconds.
Once that blood becomes oxygen depleted, it is then transported via the veins back to the heart where it can be pumped back through the lungs for a fresh supply of oxygen. Now with respect to the blood return phase, that O2 depleted blood in the lower extremities must flow upwards fighting against gravity in order to get back into the heart.
And this trip back up to the heart takes more oomph than the single pump that sent O2 rich blood downwards.
Enter the calves, whose pumping power combines with the pulling power of the heart to make that blood return process as efficient as possible.
And the process goes like this:
When we tense those calf muscles, veins are compressed thereby forcing blood upwards to the heart.
Not only that but there are valves in those veins, the venous valves, that open up to allow the O2 depleted blood to rise upwards - but not downwards.
Now in the lying position there’s minimal gravitational influence on blood flow, so an adequate level of venous return is made possible by lower gravitational pressures.
But hoist yourself up to a sitting position and that’s when venous blood in the lower torso has to return to the heart against higher gravitational forces requiring pressures well above the usual pressures in the veins.
And the best way to keep that circulation flowing properly when seated and/or standing is to move.
Because each and every time the calves contract, the calf pump helps to push blood upwards against the forces of gravity.
Don’t move the legs for long periods of time while sitting and that’s when blood and toxins can collect in the lower legs and cause swelling.
As you can see, inactivity can be a one of the biggest obstacles to the calf muscle pump working properly.
When we discontinue leg movement, we discontinue that calf pump’s ability to apply upward pressure to assist in venous return.
And the longer those calves are inactive the greater risk of blood pooling in the veins, not to mention risks of developing spider veins, varicose veins and blood clots.
Therefore it’s super important to exercise the calves. Walking, hiking, running, jogging and cycling are all activities that will keep the calf pump healthy and active.
Another way to keep the calf pump healthy is to do calf resistance work.
The larger of the two calf muscles (the muscle you see when flexing your calves), the gastrocnemius, is typically the calf muscle most often worked in the gym.
And because the gastroc’s 51% fast twitch muscle fibers it usually responds better to muscle-building than the soleus.
Two of the best gastroc exercises are the standing calf raise and the donkey calf raise.
The soleus (situated under the gastroc) is a smaller muscle. And because it consists of almost 80% slow twitch fibers, it’s a bit tougher to build up.
What’s more, the best way to work the soleus is by isolating it, and the way to do that is by performing the seated calf raise.
As you can see, any discussion about heart health has to include the second heart that obscure little muscle group called the triceps surae that helps to pump blood back up to the heart.