How Your Calf Muscle Pump Acts as a Second Heart

Every step you take, every ankle bend and every lift onto your toes sets an impressive pump in motion beneath your knees.

Your calf muscles compress the veins in your lower legs, helping to drive blood back up towards the heart. Because of their vital role in circulation, the calves are sometimes called the body's "second heart".

How the calf muscle pump returns blood to the heart

This description is only a metaphor: the calves cannot take over from the organ that beats in your chest. They do, however, help with one of the circulatory system's hardest jobs - sending blood from the legs back upwards against gravity.

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

That 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 contract. In doing so, they squeeze the nearby veins and force the blood within them upwards.

Tiny one-way valves inside the veins prevent blood from dropping back towards the feet between contractions. With every movement, blood progresses another stage on its way to the heart.

A well-functioning pump helps stop blood collecting in the legs. If it is not working effectively, ankles may swell and legs can feel sore or heavy. Reduced pump function may also play a part in long-term vein conditions.

Impaired calf pump function and health

Research indicates that poor calf pump function could provide clues about a person's broader health.

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

People with impaired calf pump function were more likely to die over the years that followed. At 10 years, mortality was about 6 percent for participants with normal pump function, versus roughly 18 percent for those with impaired function.

This does not show that weak calf muscles were directly responsible for those deaths. Instead, an impaired pump might indicate inactivity, loss of muscle, joint issues, conditions affecting muscles or nerves, or poorer overall health.

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

For this research, scientists assessed almost 6,000 patients. They found that the less blood the calf pump pushed out during movement, the greater the risk of death. Participants with the weakest pump function faced more than twice the mortality risk of people whose calves shifted blood efficiently.

This was an observational study as well. It cannot demonstrate that calf exercises lengthen life, and researchers have not yet fully explained the relationship.

Keeping the calf muscle pump active

It is straightforward to activate this pump.

Walking is the simplest option, as each step contracts the calf muscles and helps propel blood upwards. Running, going up stairs and repeatedly lifting onto the toes use the same process.

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

If standing up is not an option, flexing the ankles up and down or lifting the heels while leaving the toes on the floor can work the calf muscles.

Long periods of standing still are not automatically an improvement. When there is no movement, the muscles cannot compress the veins efficiently. A short walk, marching on the spot, or lifting and lowering the heels can help keep the pump working.

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

Ongoing swelling, or sudden pain, redness or warmth in one leg, should not simply be put down to too much sitting. They may be symptoms of a blood clot and need medical assessment.

The soleus muscle and blood sugar

Moving the calves may have advantages that extend beyond circulation.

In a small 2022 study, researchers examined a seated exercise that works the soleus, a deep calf muscle that can remain active for long periods without becoming tired.

For the "soleus push-up", the front of each foot stays on the floor while the heels are repeatedly raised and lowered.

The researchers reported that prolonged contractions increased the muscle's energy consumption and helped the body process glucose and fats after meals.

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

However, participants did the movement for lengthy periods rather than just a few repetitions, and both studies were small.

Doing a few heel raises beneath a desk is no substitute for walking, full-body exercise or any medical care that is needed. Even so, the results offer another reason to avoid staying motionless for hours.

Your calves do not truly house a second heart. Yet whenever they contract, they provide the real heart with worthwhile support.

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 let us know.