[enjeyw]

I'm naive in the space so take this with a grain of salt, but I believe the original Tabata study[0] showed comparable increases in participant VO_2 max compared to non-HIIT, with only a 4 minute workout.

Put that alongside evidence that sustained exercise (how sustained I have no idea) has negative effects (as per above comments), and the argument seems plausible.

[0] https://en.wikipedia.org/wiki/High-intensity_interval_traini...

[scruple]

I am familiar with the original Tabata study. I guess my point here is that it's been widely accepted, at least for the last decade or so (Dr. Maffetone was figuring some of this out in the early 80s, FWIW...), that HIIT (and strength training) cause concentric cardiac hypertrophy, whereas LISS primarily causes eccentric cardiac hypertrophy. I'm speaking very generally here, but... 1 increases the size of your heart, thus the volume of blood and therefore oxygen (it has to pump less to deliver oxygen to your muscles leading to a lower BPM), and the other makes your heart stronger (it can pump all of this extra blood). This is all of course a very unscientific explanation and I'm not an expert.