Well, I go in there with a plan already laid out for me. I rarely deviate from it, at least not much. Sometimes I can't quite do every rep on my plan. Sometimes my plan turned out to be too easy. I never really know for sure how it'll be until I get in there and do it. Since it's a plan for linear progress, I just stick with it. Then twice a week I do 5 minutes of one of these finishers. It's only 5 minutes. There's got to be enough left in anybody's tank to jump and flop around for 5 more minutes. I admit the walk out of the gym and back to my office sometimes feels pretty long after that.
Also, you are talking to someone who is capable of forcing herself to walk 30 miles a day for multiple days in a row on no protein. I seem to have no way of gauging what an "empty tank" feels like. There is ALWAYS more.
I'm not sure the difference between Mark's sprinting, HIIT and HIT. The way I've done sprints was to run for 15-20 seconds or so at max effort and then rest until I can do it again. The way I do these finisher things is to not rest at all between the various exercises, so it doesn't feel like intervals. The sprints might take me 15-20 minutes. The finisher takes me about 5 minutes. So they don't feel like the same thing at all. I haven't done any sprints for a long time. I kept hurting myself and remaining sore for days and days afterwards so I quit.
Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.