Today in our Bikini Body Countdown  plan, we're doing some cardio. This 45-minute workout starts at a slower place, but to keep things interesting, the speed picks toward the end, making this a negative-split run. It takes a little discipline to start slowly and build speed throughout your workout, but when the time comes to run faster, your body will be ready for the challenge. Doing this type of workout consistently will help increase your overall running speed, too. And we love that 45 minutes of cardio is going to burn some serious calories.
If running isn't your jam, try this 45-minute elliptical workout , or bike, swim, or Zumba — it doesn't matter how you get your heart rate up, just keep moving for three-quarters of an hour.