[unop]

Umm, the front-loaded 8k hours might not have much return if you were sedantary in the later decades (arguably the years where exercise helps stave off metabolic disease) as much as sustained levels of exercise all through life.

I mean, we all know of the university budding sports star types who probably invested in many hours training and trying to break into their sport professionally but not quite cutting it - and then "retiring into mediocrity" with the regular 9-5,2 hour commute, 3 kids and the diet to match. They exercise no differently to the regular Joe and suffer all the maladies the same.