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I thought Satchel Paige said it, but apparently not. He did say "I generally don’t like running. I believe in training by rising gently up and down from the bench. "
Which also fits the "don't prematurely age the stem cells"
Consider an average person's 72/min resting heartbeat. That will be (726024365.25=) 37,869,120 heartbeats per year or ~379 million/decade.
Now, add strenuous running or cycling 5 hours/week, maybe a 10mi run, and a bunch of 20-60 minute runs. Call that average 180 beats/minute. That adds ((180-72)30052=) 1,684,800 beats/year, or +16 million per decade.
The average person's 37,869,120 beats/yr divided by the exercising person's 27,349,920 yields a ratio of 1.3846. So, based on heartbeat count alone, the exerciser will live 38% longer.
BUT, this kind of training will dramatically reduce the resting heartbeat. Training far less than this, my resting heartrate declined into the high-40s-low-50s, and has remained consistent for decades of mostly maintenance training. Most recent six month average is 52 beats/min. with far less than 5hr/week training, but let's use that. That means the resting heartrate is 27,349,920 beats/year, plus the added 1,684,800 exercise beats, making it 29,034,720 beats/year or ~290 million beats per decade.
That means the exercising person 'spends' 8,834,400 FEWER* heartbeats per year, or saves 89 million heartbeats per decade.
And that level of workout will probably produce an even significantly lower resting heart rate than the 52 I cited. And for the top endurance athletes in distance running, cycling, nordic skiing, although they might spend 10+ hours/week at threshold or some training zone, so double those extra 'exercsie beats', they also often have resting heartrates in the low 40s/minute, which will yield an even greater lifespan if it is measured in heartbeate.
(This has happened to two family members that were both runners.)
It's complicated but I recommend you read up on Hormesis:
https://en.wikipedia.org/wiki/Hormesis
Cells have thresholds for what's considered to be a "good" stressor or a "bad" stressor.
Alcohol was thought to be hormetic for a long time (though, it maybe/probably isn't?) as it was thought that low doses could be beneficial with high doses obviously bad.
Exercise is thought to be hormetic and there's quite a lot of research supporting that.
Is there a net benefit?
Your resting HR becomes lower and blood has more oxygen. And this happens 24/7. Assuming you’re running 5K 2 times in a week.
https://www.cnn.com/2019/02/08/politics/donald-trump-exercis...