1. How blood is supposed to get back to the heart from the legs

Blood leaves the heart under pressure (arteries) and goes down to the legs pretty easily. Coming back up is the hard part — especially from the feet, ankles, and calves — because now the blood is moving uphill through the veins.

Your body solves that with 3 main tools:

  1. Calf muscles — especially the gastrocnemius and soleus
  2. One-way valves in the leg veins
  3. Movement (walking, ankle pumps, toe raises)

The muscle pump

  • When you walk or flex your ankle, the calf muscles squeeze.
  • Around and inside those muscles are deep veins.
  • That squeeze works like a hand milking a tube — it compresses the veins and pushes blood upward.
  • The one-way valves in the veins snap shut so the blood can’t fall back down when the muscle relaxes.

So every step you take is like a little assist to the heart. That’s why we say the calf is like a “peripheral heart” or “second heart.”

2. What happens when you don’t move much

If the calf muscles don’t contract regularly:

  • Less blood gets pumped upward.
  • Blood can pool in the lower legs (venous stasis).
  • That pooling can cause swelling (edema), heaviness, and over time skin changes or venous ulcers.
  • Sluggish blood flow raises the risk of blood clots in the legs (DVT) — and a clot can travel to the lungs (pulmonary embolism), which can be life-threatening.

So limited mobility doesn’t just make you “out of shape” — it can literally slow the circulation from the legs.

3. Why this matters for the heart itself

When the legs help return blood efficiently, the heart gets a steady supply of blood to pump (we call that venous return). Good venous return helps the heart work efficiently.

When venous return is poor (because you’re not moving):

  • The heart may have to work under less-than-ideal conditions.
  • Fluid can build up in the legs.
  • If a person already has heart failure or weakened circulation, poor leg pumping can worsen swelling and workload on the heart.

So good leg movement supports overall circulation; poor leg movement can strain an already weak system.

4. Tie-in to diabetes and amputations

You mentioned feet getting cut off from diabetes — that’s a big deal for circulation for a few reasons:

  1. Diabetes damages blood vessels and nerves. That already reduces good circulation to and from the legs.
  2. If someone gets an amputation, they often become less mobile afterward — even if they get a prosthetic, sometimes they walk less.
  3. Less walking = less calf pumping. So blood return from what’s left of the limb is reduced.
  4. Diabetes also increases the risk of infection and poor wound healing, and poor circulation makes healing worse. That can create a cycle.

So diabetes → poor vessels + less movement → worse circulation → higher heart and whole-body stress → can affect longevity.

5. Hip replacements, knee replacements, and complications

Any time someone has a major joint surgery (hip, knee):

  • They usually have a period of reduced mobility.
  • After surgery, blood is more likely to clot.
  • Combine not walking much + veins not being pumped + post-surgery inflammation → ↑ risk of DVT. That’s why doctors often give blood thinners or tell people to do ankle pumps in bed.
  • If complications happen (pain, infection, the joint doesn’t work right), people may stay chronically less active — and that long-term inactivity keeps circulation sluggish.

So it’s not just the surgery — it’s the loss of the natural calf-pump rhythm afterward.

6. Wheelchair use and the heart

If someone has to use a wheelchair:

  • They may sit for long periods with the legs below the heart, and not moving.
  • Calf muscles aren’t firing like they do during walking.
  • That leads to dependent edema (fluid pooling in the lower legs/feet).
  • Over time, chronic swelling and poor venous return can stress the cardiovascular system, increase clot risk, and reduce overall conditioning.
  • Also, when you move less, your overall fitness drops — the heart, lungs, and muscles all decondition. A deconditioned person has less “reserve,” which can shorten lifespan when illness hits.

So wheelchair use itself isn’t the problem — it’s immobility. Many wheelchair users are taught leg/ankle exercises or wear compression stockings to keep that blood moving.

7. How this connects to longevity

Longevity is about how well your circulation can keep every tissue supplied over years. If the lower half of your body becomes a low-flow zone because you don’t move:

  • More swelling
  • More skin breakdown
  • More infections
  • More clots
  • More strain on an already aging heart
  • Less ability to exercise (which protects the heart)

All of that, over time, can chip away at lifespan and quality of life.

8. Practical ways people compensate when they can’t walk much

Even for someone with diabetes, joint problems, or wheelchair use, you can still “fake” the calf pump:

  • Ankle pumps (point toes up/down repeatedly)
  • Foot circles
  • Seated marching
  • Compression stockings (help veins push blood up)
  • Elevating legs to let gravity help
  • Frequent position changes (don’t sit 4–5 hours straight)
  • Upper-body exercise to keep overall circulation strong

These don’t replace walking 100%, but they keep the “second heart” from shutting down completely.

Bottom line: The calf is called the “second heart” because every step squeezes blood up toward the real heart through one-way veins. When you stop moving — because of diabetes complications, amputations, joint replacements, or wheelchair dependence — that pump goes quiet. Quiet pump → pooled blood → swelling, clots, slower healing, more work for the heart. Over years, that can shave off health and longevity. Movement, even small movement, keeps the pump alive.