The human body. Photo Credit: SciePro/Shutterstock.
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Recently, a Facebook user, From Quarks to Quasars, claimed that the human body has a “second heart” located in the lower part of the legs.
“You have a second heart, and it lives in your calves,” the Facebook user asserted.
The user further explained that the phenomenon refers to the soleus muscle, which pumps blood from the back of the leg to the chest.
As of Aug. 12, 2025, the claim had gotten 46,000 likes, 2,900 comments, and 23,000 shares.
The phrase “second heart” has been used to describe a surprising function of the lower leg muscles, sparking interest and confusion among readers.
“Ain’t no way I’m gonna believe this. It ain’t a heart on our calves,” Maria Bautistae, a Facebook user, opined.
“I guess that’s why they say people with bigger calves live longer,” Sue Zie, another Facebook user, expressed.
As part of DUBAWA’s commitment to media and information literacy and promoting factual health knowledge, we explored the science behind the so-called “second heart ” and its significance to health.
The second heart in the body
The calf muscle is called the “second heart”. It is not an actual organ but a metaphor for the calf muscle pump. It is located in the posterior, the lower leg’s back part.
It is a system of leg muscles, especially the soleus, a powerful muscle in the lower calf, that helps you stand and walk. Veins and one-way valves also participate in this system, pushing blood from the legs back to the heart.
These muscles assist the cardiovascular system by circulating blood upward, working against the force of gravity.
When the calf muscles contract, they squeeze the deep veins in the lower legs, propelling blood toward the heart.
In a research published in the National Library of Medicine, physiologists described the calf pump as the motive force enhancing venous blood return from the lower extremities to the heart.
In particular, the soleus muscle contains a rich venous network and “contributes to the muscle pump of the lower extremity,” highlighting its key role in this pumping system.
How the calf muscle works as the body’s second heart
The calf muscle works like a built-in pump in one’s lower leg. When a person walks, runs, or even stands on their toes, the calf muscles contract, squeezing the veins and pumping blood toward the heart.
Tiny one-way valves in the veins snap shut between contractions, keeping the blood from flowing backwards.
This simple yet powerful mechanism is often called the “second heart” because it works tirelessly alongside the real heart to keep blood moving.
This system works against gravity, helping return oxygen-poor blood from the legs to the chest. Without regular calf movement, blood flow in the legs can slow down, leading to pooling and increased pressure in the veins.
Importance of the calf muscle
- Locomotion and movement: The calf muscles are essential for walking, running, jumping, and balance. They help you point your toes downward (plantarflexion) and give you the push-off power you need when moving forward.
An article from the Cleveland Clinic notes that strong calf muscles allow one to walk, run, jump, leap, and propel one forward.
Furthermore, they help to raise one’s toes, flex the feet, or straighten the legs. It acts as a key postural muscle, helping to stabilise the leg and prevent the body from tipping forward during standing.
- Cardiovascular Circulation: The calf muscle helps the blood circulate through the body. With each step, the calf muscles squeeze the veins in one’s legs, pushing blood toward the heart. This action is why the calf is often called the body’s “second heart.”
The Cleveland Clinic explains that the calf muscle acts like a natural pump. Each contraction pushes blood out of the legs and helps it move against gravity. When the muscle contracts, it compresses the veins; when it relaxes, the veins refill with blood. Vein valves keep the blood flowing in the right direction.
Research shows that a single contraction of the calf muscle pump can push 40 to 60 per cent of the blood into the leg veins. Something as simple as a few heel raises while walking can significantly reduce venous pressure from about 100 mmHg to 22mmhg, making circulation more efficient.
- Prevention of injury: The last role of the calf muscle is to prevent injuries. Strong, well-conditioned calf muscles do more than power movement; they also help protect the legs and the body from specific health problems.
The calf pump prevents swelling and clotting by supplying blood flow. When the calf muscles are inactive for long periods, circulation slows down, increasing the risk of chronic venous insufficiency. Research warns that poor calf pump activity can contribute to conditions like varicose veins and Deep Vein Thrombosis (DVT).
Consequently, clinicians often recommend simple physical activities to keep the calves engaged, such as walking or flexing the ankles. Every time the calf muscles contract, they send blood back toward the heart, lower the pressure in the leg veins, reduce fluid buildup in the tissues, and prevent problems like edema and blood clots.
Experts’ Opinions
DUBAWA spoke to Michael Ogirma, an Orthopaedics and Trauma Surgery professor at Ahmadu Bello University. When asked to explain how the calf muscles help the heart pump blood and why this is important for overall health, he said the calf muscles are regarded as the “second heart” because within them are blood vessels.
He says, “The more you move around, the more the calf muscles contract. The calf muscles aid in pumping blood from the legs back to the heart. Life is movement, and movement is life.”
He noted that if one does not move around, the blood vessels in the calf might detach and go and block the blood vessels supplying the heart (thromboembolism phenomenon). He advised using the calf muscles to avoid this phenomenon.
DUBAWA also spoke to Lateef Thanni, an Orthopaedic Surgery professor at Olabisi Onabanjo University. We asked about the most effective ways for people, especially those who sit or stand for long hours, to keep their calf muscles pumped and healthy and prevent circulation problems. He advised one to avoid sitting for more than two hours at a stretch.
“If you must sit, keep tiptoeing or flexing your feet so it pumps blood back to the heart,” he said.
He added that simple exercises can prevent many health issues, and recommended staying hydrated, engaging in rigorous walking, and exercising at least three times a week.
Conclusion
The calf muscles do far more than help us walk; they act as a vital “second heart,” keeping blood moving and reducing strain on the heart. Staying active is the simplest way to keep this silent pump working and protect your health.
