I have met people who figured, because they don't excercise they don't wear their body out, so their joints etc. will last longer. Same for injury, no sport no injury, that must be good!
In a way this is right with high intense/extreme sport. (I did Thai Boxing in my youth, but stopped at some point)
But it is very wrong otherwise, joints for example will suffer if not moved. Blood will only flow into all the areas of the joints if they are moved. And if you don't move, your muscles will be gone and without muscles to hold your joints, loss of stability, great risk of injury, etc.
I got codex to count my total heartbeats from my Garmin data. For four random days the counts were 72.252, 73.823, 68.922, 70.991.
According to google: "typical range for total heartbeats is 86,400 to 115,200 beats per day"
I run every day which would add a lot of beats, but my resting HR is 36 (pushed down by exercise i presume) with a daily average of 50 BPM. So in total a trained person may spend less of their heart beats.
Most people who talk about adding milage to a car have never tried to keep an old car running. Those who do have long learned that milage is a tiny issue, age is a much larger factor. They have also learned that low milage is a bad sign - what is wrong that you only drove it that much: often the answer is city driving which puts a lot more wear on the car than highway driving.
People who exercise regularly have a lower resting heart rate. You can likely remove 10,000 heartbeats per day just by doing 20 minutes of exerciser per day.
I don't believe the limited heartbeats theory, but it does support the idea of exercise.
But it is very wrong otherwise, joints for example will suffer if not moved. Blood will only flow into all the areas of the joints if they are moved. And if you don't move, your muscles will be gone and without muscles to hold your joints, loss of stability, great risk of injury, etc.