This workout is probably my favorite treadmill run. It will definitely leave you dripping sweat and breathing hard. Honestly, I really didn’t like running on a treadmill until my best friend at college and I started to do high-intensity-interval-training on the treadmill. I would usually opt for the elliptical, but HIIT provides much more of a workout. This was our go-to run, we were always trying to get more than three rounds. And I still love it!