What, the whole left ventricle hypertrophy thing? (or whatever)
Its probably a thing, but I think if it had a severe effect, we would have seen "the data" on that materialize already.
Xfit caught fire in 2008-2012 ish? ...mostly 30-45 year olds from what I've seen.
Those peeps are 42-60-ish by now. I would think some data would've surfaced by now.
ehh, even if that pans out and they die a little early from a weirdo heart problem, maybe if they stick with their X-fit-esque HIT workouts while they're alive they are living a better life (healthspan vs lifespan thing).
But overall, I agree: people doing "heavy" weight training (or bodybuilder rep & set training /schemes ) are kinda already doing a form of quasi-HIT work, and should be doing some LISS cardio as their standard form of cardio. Not HIIT.