im 21 5'10" 195. my HIIT routine is 5 min warm up @ 3.5, then 1 min run @ 9, then 2 min @ 3.5, and 1 min run @ 9 x 10. this is on a treadmill. My hearbeat is at 175-180 when im running, goes as low as 135 after a minute of speed walking at 3.5. according to the chart at my gym 135 is in the low intensity fat burning zone, and the 175 is in the high intensity cardio mode i do this for about 40 mins. i am on a cutting phase right now. i do the routine 3 times a week, and lift in between. I drink a protein shake right after, and i usually HIIT 1st thing in the morning fasted. Thoughts, suggestions?