Scientists have found a "second heart" in the human body

Most people believe that only the heart is responsible for blood circulation. However, the calf muscles also play an important role in this process. Every step, standing on your toes, or even simply bending your foot helps the blood to rise from your feet back to your heart, overcoming gravity.

That is why caviar is often called a "second heart." Although this is only a figurative expression, research shows that the work of this muscle "pump" can be related not only to the condition of the veins, but also to the general health of a person. How the "second heart" works, what is the danger of sitting for a long time and why regular walking is considered one of the best ways to support blood circulation — in the Izvestia article.

How calves help the heart pump blood

The heart easily directs oxygenated blood to the legs through the arteries. However, it is much more difficult to bring it back: the venous system has to lift the blood up against gravity, while the pressure in the veins is much lower than in the arteries. Unlike the heart, the veins themselves are not capable of creating a powerful pumping force. The mechanism is described in detail in the journal ScienceAlert.

This is where the so-called calf muscle pump comes into play. When a person walks, runs, climbs stairs, or just stands on his toes, the muscles of the shin contract and squeeze the deep veins. Under the influence of this pressure, the blood moves upward to the heart, and special venous valves do not allow it to drain back. Therefore, each movement actually helps the cardiovascular system maintain normal blood circulation.

The term "second heart" does not mean that the calf muscles can replace a real heart pump. This is just a physiological analogy, emphasizing their importance for venous blood return. If the muscle pump is working efficiently, the blood does not stagnate in the lower extremities. If its function is disrupted, there may be heaviness in the legs, swelling, soreness and other manifestations of chronic venous diseases.

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What research says about health and life expectancy

Scientists' interest in the calf muscle pump is not only related to its effect on blood circulation. In 2020, Mayo Clinic specialists analyzed the data of 2,728 patients who underwent vascular examination. The results were published in the journal Vascular Medicine. It turned out that in people with impaired calf pump function, mortality over the next ten years was significantly higher than in patients with normal operation of this system.

The results were later confirmed by a larger study published by the Mayo Clinic in 2024. It included almost 6 thousand people and showed that the less blood the calf muscles are able to move upward during contraction, the higher the risk of death in the future. In people with the most severe impairments, this indicator was more than twice as high as in participants with a well-functioning muscle pump.

At the same time, the researchers emphasize that such work is observational in nature. They do not prove that weak calf muscles themselves cause death. Most likely, the poor functioning of the muscle pump reflects the general state of human health. It can be associated with low physical activity, age-related loss of muscle mass, diseases of the nervous system, joints or blood vessels.

Nevertheless, experts believe that the function of the calf pump can become an additional marker of the state of the cardiovascular system and general physical health, especially in the elderly.

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Why sitting for a long time is harmful even for healthy people

The easiest way to keep your "second heart" functioning is to move regularly. Each step activates the calf muscles and helps the blood return to the heart. Running, climbing stairs, walking on your toes, and many other habitual movements have the same effect.

Problems arise during prolonged immobility. If a person sits at a desk for hours or stands motionless for a long time, the muscles practically stop contracting, which means that the venous pump works less efficiently. As a result, the blood begins to stagnate in the lower extremities, the pressure in the veins increases, a feeling of heaviness and swelling appear. If other risk factors are present, it may also increase the likelihood of developing chronic venous insufficiency or deep vein thrombosis.

That's why the American Heart Association recommends getting up from your desk at least once an hour and walking a bit. If this is not possible, experts recommend periodically moving your feet up and down or lifting your heels several times without lifting your socks off the floor. Even such simple movements allow you to activate the calf pump.

Doctors also remind you that sudden pain, redness, a feeling of heat or pronounced swelling of one leg should not be attributed solely to a sedentary lifestyle. Such symptoms may indicate deep vein thrombosis and require medical evaluation.

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Can a "second heart" affect your metabolism?

In recent years, scientists have been studying not only the effect of calf muscles on blood circulation, but also their possible role in metabolism. Of particular interest is the soleus muscle, a deep muscle of the shin that can work for a long time without significant fatigue.

In a 2022 study published in the journal iScience, participants were asked to perform a special exercise called the soleus push-up. During it, a person, sitting on a chair, repeatedly raises and lowers his heels, without lifting his socks from the floor. The authors found that prolonged work of the soleus muscle increases energy expenditure and helps the body process glucose and fats more efficiently after eating.

Later, a small pilot study in Sports magazine involving people with prediabetes showed that doing this exercise during a two-hour glucose tolerance test reduced blood sugar levels by about a third compared to regular sitting. However, the scientists emphasize that both studies were small, and the participants performed the exercise for a long time, so it's too early to talk about the therapeutic effect.

The authors note that several heel lifts under the desk will not replace full-fledged physical activity, walking or medical treatment. Nevertheless, the results provide another argument in favor of regular movement and show that even relatively small muscles can play a much more important role in the body than previously thought.