how come the ones who live the longest never do the HIIT treadmill hamster wheel training, but rather frequent light-to-moderate walks, bicycle rides, garden work or the like?
Re your observations. Are you referring to elderly people? I'm not sure this study is about them. My mental model of this mechanism is that relatively young people can choose between e.g. long distance running and sprinting, and that the latter will yield better cardiac outcomes.
https://en.wikipedia.org/wiki/Bioenergetic_systems#ATP%E2%80...
But if you do 30-60s work intervals treadmills work just fine.
The treadmill also wasn't able to change speeds fast enough to really do the good Sprint simulations