If you do it, what's your HIIT routine & how many times a week do you do it? Just curious, not trying to compete, as I know it's different depending on your fitness level.
For now, I'm trying 1 min sprint runs of a speed of 5 every 5 minutes on my treadmill. After the 1 minute I do a brisk recovery for 4 mins on 3.5, and then repeat.
What's yours? And how often do you change it up if you've been doing it for awhile? I used to do just walking and my treadmill would handle cranking up the incline and speeds for me on a predetermined sequence, but I decided I wanted to challenge myself with run sequences.