18 May The Calf Muscles: The Body’s “Second Heart”
The calf muscles are often described as the body’s “second heart” — and for good reason. Every step, ankle movement, and calf contraction helps push blood and lymphatic fluid back toward the heart against gravity.
Without this system, blood and fluid would begin to pool in the lower legs. Swelling would increase, circulation would slow, and problems such as varicose veins, chronic leg swelling, and tissue damage would become far more common.
From a clinical perspective, the calf muscle pump sits at the centre of many common conditions, including chronic venous insufficiency, oedema, venous ulcers, deep vein thrombosis (DVT), lymphedema, and immobility-related swelling. In practical terms, healthy calf function is essential for healthy circulation.
Why the Legs Need a “Second Heart”
Blood is delivered to the legs by the heart through the arteries under high pressure. Returning that blood is much more difficult.
Veins in the feet and lower legs must move blood upward against gravity under relatively low pressure. When standing still, pressure in these veins can rise significantly due to the weight of the blood column above them.
Without an effective pumping mechanism, blood quickly begins to stagnate in the lower limbs.
This is where the calf muscles play a critical role.
How the Calf Pump Works
The calf muscle pumps that surround the deep veins of the lower leg. When these muscles contract during walking or ankle movement, they compress the veins and help push blood upward toward the heart.
Inside the veins, one-way valves ensure that blood flows in a single direction. As the muscles squeeze the veins, blood is propelled upward; when the muscles relax, the valves prevent it from flowing back down.
Each time the calf muscles relax, pressure inside the veins drops, allowing them to refill before the next step. This repeated cycle creates an efficient pumping system that operates with every movement.
In healthy individuals, walking can significantly reduce venous pressure in the lower legs, which is essential for normal circulation and tissue health.
What Happens When the Calf Pump Weakens
When the calf muscles are weak or inactive, venous return becomes less efficient. Blood remains in the lower limbs for longer, and pressure inside the veins stays elevated, particularly during standing and walking.
Over time, this contributes to a range of problems, including varicose veins, leg swelling, skin changes, heaviness, aching, venous ulcers, and poor wound healing.
Calf pump dysfunction is commonly seen in people with reduced mobility, sedentary lifestyles, neurological conditions, obesity, or after surgery. Even reduced ankle movement alone can significantly impair circulation in the lower legs.
This is why regular movement is so important for vascular health.
The Calf Muscles and the Lymphatic System
The role of the calf muscles extends beyond blood flow. They are also essential for lymphatic drainage.
The lymphatic system does not have a central pump like the heart. Instead, it relies on body movement, muscle contractions, breathing, and one-way valves to move lymph fluid through the body.
This lymphatic fluid contains water, proteins, immune cells, and waste products that must be cleared from tissues.
The calf muscles are one of the most powerful drivers of lymphatic flow. When they contract, they compress lymphatic vessels and push fluid upward through the legs. When they relax, the vessels refill and collect more fluid from surrounding tissues.
Walking therefore functions as both a venous pump and a lymphatic pump.
This dual role explains why immobility often leads to both swelling and fluid congestion in the lower limbs.
Movement as a Circulatory Requirement
The venous and lymphatic systems depend heavily on movement. They function most effectively when the body is active.
Even small reductions in walking or ankle mobility can reduce the efficiency of the calf pump. Over time, inactivity has a significant impact on lower limb circulation.
This pattern is commonly seen in older adults, post-operative patients, sedentary individuals, and people with chronic venous disease.
In simple terms, reduced calf function leads directly to reduced fluid return from the legs.
Supporting the Calf Pump
Improving calf muscle function is one of the most effective and accessible ways to support circulation.
Regular walking remains the most important intervention. Calf raises, ankle mobility exercises, compression therapy, early mobilisation after surgery, and mechanical compression devices can all help improve the efficiency of the calf pump.
Neuromuscular electrical stimulation (NMES) is particularly effective, especially in individuals with reduced mobility or impaired calf function. By delivering controlled electrical impulses via the calf muscles, NMES induces rhythmic muscle contractions that mimic the natural pumping action of walking. This helps compress the deep veins, increase venous return, and reduce venous stasis and oedema10, even in the absence of active movement. It is especially valuable in post-operative patients, those with neurological impairment, or individuals who are bedbound or highly sedentary, where voluntary calf activation is limited or inconsistent.
In clinical practice, a proven example of NMES is the geko® device. It delivers gentle neuromuscular electrostimulation to the common peroneal nerve, activating the calf and foot muscle pumps, increasing venous, arterial and microcirculatory blood flow, at a rate equal to 60% of walking in immobile or post-surgical patients – without the patient having to move. www.gekodevices.com
Conclusion
The calf muscles are far more than muscles used for movement. They are a vital part of the circulatory system.
By helping return blood and lymphatic fluid to the heart, the calf pump protects the lower limbs from swelling, congestion, inflammation, and long-term tissue damage.
In many ways, the calf truly functions as a “second heart.”
Maintaining regular movement, ankle mobility, and calf strength is therefore fundamental to long-term vascular and lymphatic health.
Click to view: The Calf Muscles: The Body’s “Second Heart” animation
References:
- Keijsers JMT, et al. A 1D pulse wave propagation model of the hemodynamics of calf muscle pump function. International Journal for Numerical Methods in Biomedical Engineering. 2015.
- Recek C. Calf pump activity influencing venous hemodynamics in the lower extremity. International Journal of Angiology. 2013;22(1):23–30.
- Williams KJ, et al. The calf muscle pump revisited. Journal of Vascular Surgery: Venous and Lymphatic Disorders. 2014;2(3):329–334.
- Uhl JF, Gillot C. Anatomy of the veno-muscular pumps of the lower limb. Phlebology. 2015;30(3):180–193.
- Scallan JP, et al. Lymphatic system flows. Annual Review of Fluid Mechanics. 2016;48:529–563. (Reviewed mechanisms of lymphatic transport and reliance on external forces such as muscle contraction)
- Barnhart H. Live to Move and Move to Live: The Health of the Lymphatic System Relies on Mobility and the Foot and Calf Pump Connection. Lymphatics. 2024;2(2):43–49.
- Orr L, et al. Exercise intervention for calf muscle pump impairment in chronic venous insufficiency: systematic review and meta-analysis. Ostomy Wound Management. 2017;63(8):30–43.
- Gloviczki P, et al. Handbook of Venous and Lymphatic Disorders. American Venous Forum Guidelines. CRC Press; 2017.
- NCBI Bookshelf. Pathophysiology and Principles of Management of Varicose Veins. (Venous return and calf muscle pump physiology).
- Sallent A, Abidi N, Baduell A, Patel S, et al.
Activation of the venous muscle pump by neuromuscular stimulation of the common peroneal nerve reduces postoperative oedema in the foot and ankle.
medRxiv / preprint (2025); Clinical trial NCT04927234.
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