If you only have a short window to spare for a workout, try this challenging 20-minute treadmill routine. Beyond switching up the speed every two minutes, you'll also be changing the incline, which challenges the body to work even harder. Even after this short cardio session, you'll feel light, energized, and ready to power through the rest of your day.
Before you head for your run, be sure to print this workout  to bring to the gym with you!
Related: 20-Minute Abs and Arms Blast