Check your grammar now! : intense or paroxysmal excitement; especially : the rapid pleasurable release of neuromuscular tensions at the height of sexual arousal that is usually accompanied by the ejaculation of semen in the male and by vaginal contractions in the female.
So, even though you may have only burned 250 calories during your HIIT workout, the total calories burned after will be far greater. Those calories, plus the 250 burned during the HIIT workout surpasses the 400 burned during the slow, steady-state workout by a LONG, LONG way.
You're ready for HIIT workouts if you've been running four to five times a week for at least four months, regularly doing some runs at paces 60 to 90 seconds per mile faster than easy pace, and completing a weekly long run of at least 50 minutes.