Why Your Calf Muscle Pump Is Called the Body's Second Heart

Every step you take, ankle bend, or lift onto the balls of your feet sets a remarkable pump working beneath your knees.

The calf muscles press on the veins in the lower legs, helping to drive blood upwards towards the heart. Because this action is so significant for circulation, the calves are sometimes called the body's "second heart".

That label is a metaphor, of course. Calves cannot take the place of the organ that beats in your chest. They do, however, support one of the circulatory system's hardest jobs: getting blood back from the legs against gravity.

The heart sends oxygen-rich blood throughout the body via the arteries. Once it reaches the legs, the blood has to return through veins, where pressure is far lower. Veins, unlike the heart, cannot create a strong pumping action of their own.

How the calf muscle pump returns blood to the heart

This is the role of the calf muscle pump.

As you walk, run, or raise your heels, the muscles at the back of the lower legs tighten. This squeezes the nearby veins, forcing the blood within them upwards.

Tiny one-way valves in those veins prevent blood from dropping back towards the feet between contractions. With every movement, blood moves a little further on its journey towards the heart.

A properly functioning pump helps stop blood from collecting in the legs. If it is not working well, swollen ankles, heavy or aching legs may result. Reduced pump function can also play a part in longer-term vein disorders.

Research indicates that poor calf pump performance could also signal aspects of a person's broader health.

In a 2020 study, researchers reviewed the medical records of 2,728 adults who received vascular testing in the Mayo Clinic's vascular laboratory in Minnesota.

During the years that followed, people with impaired calf pump function were more likely to die. At the 10-year point, mortality was approximately 6 percent in people with normal pump function, versus around 18 percent in those with impaired function.

This does not show that weak calf muscles themselves caused the deaths. A poorly functioning pump may instead indicate inactivity, loss of muscle, joint conditions, illnesses affecting muscles or nerves, or poorer health overall.

A larger 2024 study from the same Mayo Clinic reinforced this association.

For this research, scientists assessed almost 6,000 patients. They found that death risk rose as the amount of blood expelled by the calf pump during movement fell. Participants with the weakest pump function faced more than twice the mortality risk of those whose calves moved blood efficiently.

This was an observational study too. It cannot establish that training the calves will lengthen a person's life, and researchers do not yet completely understand the link.

Keeping the calf muscle pump active

It is straightforward to activate this pump.

Walking is the simplest option: every step contracts the calf muscles and assists blood flow upwards. The same system is engaged by running, climbing stairs, and repeatedly lifting yourself onto your toes.

Those with desk-based jobs should not stay in the same position for hours. The American Heart Association advises getting up and walking about at least once every hour.

If standing up is not an option, pointing and flexing the ankles, or raising the heels while keeping the toes on the ground, can still activate the calf muscles.

Prolonged standing is not automatically an improvement. When you remain still, the muscles do not compress the veins efficiently. Walking a few paces, marching on the spot, or lifting and lowering the heels can maintain the pump's activity.

Routine exercise may also help maintain calf strength as you get older. The World Health Organization advises at least 150 minutes of moderate-intensity physical activity each week, such as brisk walking, plus muscle-strengthening exercise on two or more days.

Ongoing swelling, or sudden pain, redness, or heat in one leg, should not be dismissed as the result of sitting too long. They may be symptoms of a blood clot and need medical assessment.

The soleus push-up and metabolism

Calf activity could have effects beyond circulation.

In a small 2022 study, scientists examined a seated exercise that activates the soleus, a deep calf muscle that can work for extended periods without becoming tired.

In the "soleus push-up", the front of each foot remains on the floor while the person repeatedly raises and lowers their heels.

The researchers reported that prolonged contractions raised the muscle's energy use and supported the body's processing of glucose and fats after a meal.

A later pilot study of only 10 people with prediabetes found that carrying out this movement during a two-hour glucose tolerance test cut the blood sugar rise by about one-third compared with remaining seated and still.

However, participants did the exercise for long stretches rather than merely a few repetitions, and both studies were small.

Doing a few heel raises beneath a desk is not a substitute for walking, full-body exercise, or any medical care that is needed. Even so, these findings offer another reason to avoid being motionless for hours.

Your calves do not literally house a second heart. Yet whenever they contract, they provide the real one with useful assistance.

This article was fact-checked by Clare Watson and edited by Clare Watson. Although we take pride in our process, we are only human. If you notice an error, please tell us.