Spice up your cardio and target belly fat with intervals! This 30-minute treadmill workout plays with speed and changes minute to minute. And switching speeds like this not only improves your overall running stamina, but it also increases the calories you burn when the workout is over.

As always, feel free to adjust the speed up or down as necessary; just make sure you're challenging yourself. If you're looking to try running intervals but want to start a little slower, try this beginner's interval plan.

Click here for a printable version of this workout.