HIIT is a technique that alternates between high intensity exercise and short rest.

It is said that HIIT is more efficient to burn a fat than running and anti-aging.
The best balance of exercise and rest is 2 : 1.(the too much rest you take, RFU is not stimulated. Besides, the longer you do exercise, it going to be overwork.)

https://journals.lww.com/nsca-jscr/fulltext/2014/04000/sex_specific_responses_to_self_paced,.7.aspx