The heart is most likely to malfunction when placed under more stress acutely than it is used to. An 80 year old who does the stair stepper is much less likely to have a heart attack walking up stairs at home because his heart is working at a lower percentage of its maximum at that point compared to someone who does not work out.
Another important note is that the idea that a heart has a certain number of beats before it gives out is old and pretty silly nowadays. Obviously some beats are different than others, and heart structure/function/energy requirements can alter throughout life.
So with regards to this, could someone answer a followup question to what we’re hearing – If you medicinally take stimulants like ADHD medication etc., does this have a similar exercising effect on your heart, or is it more like performance doing damage to it, similar to pistons on a sports car engine?
By ‘finite’ I’m guessing you mean the often quoted statistic that [our hearts beat a certain number of times before they conk out.] (https://www.google.com/amp/s/www.sciencealert.com/relationship-between-heart-beat-and-life-expectancy/amp)
There’s two things here. First of all, others have touched on ‘resting heart rate’. The better shape your heart is in, the less frequently it has to beat when you’re at rest. So if we were counting heartbeats, then the heartbeats you ‘spend’ working out, you’ll generally make up for while resting.
That said, the number of heartbeats isn’t what determines when your heart stops working. However, your heart rate is very very tied to your overall health. So you can think of your heart rate as a kind of predictive timer.
Say I use Google maps to figure out how long it’ll take me to get to work. It predicts half an hour. It knows this because it’s synced up with all the things that will speed me up or slow me down. I get to work half an hour later. Google maps’ time prediction didn’t help me *get* to work. It just predicted.
We evolved for survival. Are bodies survived by doing certain things that benefited us. One of the things we used to do to survive was move around a lot. Our system is adapted to be healthy when we move. Even though we don’t move as much now, our body is still adapted for maintaining itself by movement. Think of working harder as “maintenance” for long term use.
For example, our lymph system (immune system) is made of one-way valves that circulate with movement. No movement leads to poor circulation which leads to lower immune response. This is just one example of many parts of us that is adapted for the environment we once lived in for a very long time.
Since the heart is just a complex muscle, it’s the same principle as with your biceps or leg muscles. When you work out, the seperate muscle fibers get damaged and have little rips or are just exhausted. When you take a break, your body panics and takes action to help you heal as quickly as possible. In the process, the fibers are made extra strong and sometimes new ones are created. It’s kind of a “One step back, two ahead” thing.
People have addressed the muscle part of it in other comments but there is also another reason. When you exercise, certain hormones are released that relax your blood vessels so that you can move blood more efficiently. Over time as you exercise more and more this makes your blood vessels more limber in general which causes you to have a healthy blood pressure in general. A normal blood pressure for longer periods of time puts less stress on the vessels which means you won’t pop an artery at 40.
Your heart is a muscle so you can think of it similarly to weightlifting. The more you work the muscle the stronger it gets. In the case of your heart, a stronger heart is more efficient and doesn’t have to pump as much when at rest. Marathon runners for instance have a much lower resting heart rate because their hearts are more efficient. There are even some mega-marathon runners with heart rates as low as 40bpm as compared to the average of about 60bpm.
It’s a muscle, working it out in a controlled fashion makes it stronger and more efficient for all the time you aren’t intentionally working it harder.
You are effectively making it’s work 90% of the time easier by working it harder 10% of the time, instead of making it harder 100% of the time.
Take professional athletes for example, they often have a resting heart rate anywhere from 40-60 beats per minute at rest. The average resting heart rate for a moderately or less-active person is usually around 60-100 depending on multiple factors. Take sleep for example, assuming 8 hours that means a normal persons heart will beat maybe 28,800 times during sleep (assuming 60bpm though it’s probably lower because you’re sleeping), an athlete’s heart will beat only about 19,200 times during sleep (assuming 40bmp, though again probably less during sleep).
Factor that in to the amount of time you are at rest vs exercise over your lifetime, even with hours of exercise regularly the athletes heart is going to come out with fewer beats over time.
Kind of the same way if you worked a hard labor job for a day it makes you appreciate that desk job a little more. Your hearts like complacently pumping the repetitiveness could give strain until you start working out and your hearts like “oh fuck what is this i hate this” then when youre done the regular pumping doesnt seem so bad anymore and its actually a relief