Your heart has a surprisingly helpful assistant — and it is probably under your desk right now.
Every time you walk, climb a staircase or rise onto your toes, your calf muscles squeeze the veins in your lower legs. This pushes blood upward, helping it return to your heart. The action is so important that the calves are sometimes called the body's "second heart."
The name is only a metaphor. Your calves cannot take over the work of the organ in your chest. But without their help, your circulatory system would have a much harder job.
Working against gravity
Your heart sends oxygen-rich blood around the body through arteries. Once that blood reaches your feet and legs, it must travel back upward through veins.
Here it faces an obvious obstacle: gravity.
Veins operate under much lower pressure than arteries, so they cannot force blood upward on their own. Instead, movement provides the extra push. When the calf muscles contract, they press against nearby veins. Small one-way valves inside those veins prevent the blood from falling back between contractions. Each step moves it a little closer to the heart.
If this muscle pump is not working effectively, blood may collect in the lower legs. That can contribute to swollen ankles, aching legs and a feeling of heaviness.
Simply standing is not enough. If you remain motionless, the calf muscles are not repeatedly squeezing the veins. From the pump's point of view, standing still can look surprisingly similar to sitting still.
A pump — or a warning light?
Research suggests that calf pump function may also provide clues about a person's wider health.
In a 2020 study, researchers examined 2,728 patients who had undergone vascular testing at the Mayo Clinic. Ten years later, about 6 percent of those with normal calf pump function had died, compared with roughly 18 percent of those whose pump function was impaired.
A later study involving nearly 6,000 patients found a similar pattern: The less blood the calf pump moved during exercise, the higher the participants' risk of death.
These findings sound alarming, but they do not prove that weak calves directly shorten a person's life — or that performing heel raises will extend it. Both studies were observational. Poor calf pump function may instead be a sign of physical inactivity, muscle loss, joint difficulties or generally weaker health.
In other words, the pump may be partly a cause of circulatory problems, partly a result of other conditions, or simply a useful warning light. Scientists do not yet have a complete answer.
Keep it moving
Fortunately, activating the calf pump requires no special equipment. Walking is one of the easiest methods. Running, climbing stairs and repeatedly rising onto your toes also make the calf muscles contract.
If you are stuck at a desk, try moving your ankles up and down or lifting your heels while keeping your toes on the floor. These small movements are useful when standing up is impossible, but they should not be treated as a replacement for walking or regular whole-body exercise.
Some early research suggests that sustained seated heel raises may also help the body process glucose and fat after meals. However, the studies were small, and participants performed the movement for extended periods — not merely five casual repetitions beneath a desk.
The practical message is much simpler than the "second heart" nickname makes it sound: Your legs were designed to move. Every walk to the kitchen, flight of stairs or impatient bounce on your toes gives your real heart a small but valuable helping hand.