Which organ is called second heart of the body? Everything you need to know about it

The calf muscle is called the second heart of the body. It is a bulging muscle located at the back of the lower leg and is made of soleus and gastrocnemius muscle.

In this article, we will try to understand why calf muscles are called 2nd heart of the human body and what their function is. So, let’s get started.

Why are calves the second heart?

Why calves are called the 2nd heart of the body? Because, both our heart and calf muscles are important pumping machines in our body.

It is interesting that if our first heart is in the upper part of the body, inside the chest, the second heart is down the leg. This is the soleus muscle, a bulky muscle on the back of the lower leg, also commonly termed the calf muscle.

The heart is a pumping machine; it pumps blood to every corner of our body to supply oxygen and other nutrition to the cells transported by the blood. However, this blood-pumping mechanism is also present in the bulk of the calf muscle, which pumps back the blood from the lower body towards the heart.

Our calve muscles consist of the soleus muscle, a thick, bulky, solid muscle behind both lower legs. Just palpate your calf muscle and feel its bulkiness and its grandiosity. This muscle is perhaps the bulkiest and most hard-working muscle in our body.

It is even bulkier for sportspersons and athletes. When I treat hockey students at our local hockey academy, I feel ashamed to compare my calf muscles with theirs. However, our calf muscle has another essential function to carry out.

Our calf muscles contract and relax when we take a step, climb stairs, or engage in any physical activity involving our lower limbs. This rhythmic action acts as a pump.

Our body is engineered such that when we do these activities, our calf muscle acts like a pump and pushes back deoxygenated blood to the heart¹. This function is essential for maintaining healthy circulation, especially in the lower extremities, and it prevents blood from stagnating or pooling in the veins.

Why is it Important?

Think of your actual heart as a powerful central pump pushing blood outwards. But without the calf muscle pump assisting in the return journey, blood would pool in your legs, leading to swelling, discomfort, and even health complications.

The process of pushing back blood by the second heart is known as venous return. It propels the deoxygenated blood from the body’s extremities back up to the heart, where it is purified and pumped out to nourish the body. Healthy venous return is important as it prevents issues such as deep vein thrombosis (DVT), varicose veins, and venous insufficiency.

Venous insufficiency leads to leg swelling. This explains why our feet and lower legs become slightly swollen after driving long distances or sitting in a plane for hours. As there is no walking, there’s no calf pumping action, resulting in fluid pooling in the legs.

Here, I have summarised the importance of the second heart:

• Improved Circulation: It aids in returning blood to the heart, ensuring proper oxygen and nutrient delivery throughout the body.
• Reduced Risk of Blood Clots: Keeping blood flowing, minimizes the chances of blood clots forming in the legs, a serious health concern.
• Enhanced Lymphatic Drainage: It promotes lymphatic drainage, which helps remove waste products from the body.
• Improved Athletic Performance: Efficient blood flow allows muscles to receive more oxygen, enhancing endurance and performance.

How to keep your second heart strong

Just like your actual heart, your second heart needs care and attention. Here are some ways to keep it pumping strong:

• Stay Active: Regular exercise, especially activities that engage your calf muscles, like walking, running, and swimming, is vital.
• Maintain a Healthy Weight: Excess weight strains your circulatory system, including your second heart.
• Wear Compression Socks: These can help improve circulation, especially if you sit or stand for extended periods.
• Stay Hydrated: Drinking plenty of water keeps your blood thin and easier to pump.
• Stretch Regularly: Stretching your calf muscles helps improve flexibility and circulation.

Also read: Calf Muscle Pain? Two exercises for quick relief

An important point on the second heart

Please note that in a pure medical term second heart actually refers to the cisterna chyli located in the abdomen, it receives the lymphatic fluids of intestine and up from the abdomen¹. However, in common sense, the second heart is referred to as calf muscle; here, in this article, we have covered the calf as a second heart.

Now that we know it’s because of the pumping action of blood, our calf muscle is termed the second heart. However, a modern-day stagnant lifestyle that limits the use of soleus muscle results in sluggish blood circulation. Healthy blood circulation is a secret of a healthy body. This is why every doctor recommends daily exercise and stretching for a healthy and fit body.

Keep reading: Why is it important to warm up before exercise & workout

Sunit. S. Ekka

Dr Sunit Sanjay Ekka is a physiotherapist in practice for the last 15 years. He has done his BPT from one of the premium Central Government physiotherapy colleges, ie, SVNIRTAR. The patient is his best teacher and whatever he gets to learn he loves to share it on his Youtube channel and blog.