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.
With HIIT, it's most effective to go four weeks on, followed by four weeks without it. During your HIIT-less cycle, focus strictly on hypertrophy to promote mitochondrial biogenesis and an increase in the nuclei effect. When your nuclei density is greater, you can make your muscle fibers larger.