Odd timing. I actually just saw this episode this afternoon with some friends.

For what it's worth, they were doing 20 second sprints. And it seemed like only a couple of them were doing it at a "12", a couple of people were standing still on the treadmill, and more than one ended up grabbing the handrails and windmilling their legs for a few strides. Given all of that, I don't find it impossible to believe.

I do think that the show's producers apply of a lot of creative editing to get the storylines and "drama" that they want, but that's true of all reality television. *shrug* Just my two cents.