Intervals help fight belly fat and increase your running endurance — both noble goals in our Better-Body Challenge . In this ladder run, the speed intervals increase in duration as the workout progresses to push your endurance, raise your heart rate, and rev your metabolism. As always, do adjust the speed as needed, but stay true to pushing the pace for yourself. Here's a 30-minute elliptical workout  with intervals if running is not an option for you.
Click here for an image-free, printable  version of the workout.