"Second heart" refers to the soleus muscle, a deep calf muscle that supports venous return the movement of blood from the lower legs back to the heart. When it contracts, it compresses deep veins, pushing blood upward against gravity. The term appears in published literature, including a 2013 International Journal of Angiology paper on calf pump activity and venous hemodynamics (PMC3699225) it's a physiological description, not a marketing term.
Not a device: if you're searching because of a pacemaker, VAD, or artificial heart, this isn't that. And the term is descriptive, not literal your heart remains the primary pump; the soleus supports circulation, it doesn't replace it. Read the full explanation →
When you sit with your knees at 90 degrees, the soleus becomes substantially less active, the calf pump slows, and venous return decreases which may contribute to heaviness, swelling, or fatigue by end of day. What happens when it stops moving → · Heavy legs after sitting →
Educational purpose only. This glossary entry is for informational purposes and is not medical advice. The term "second heart" refers to the soleus muscle, not a medical device.