Celebrities are known for trying a wide range of wacky health trends. (Remember the Master Cleanse craze, circa 2008?) So it makes sense that stars have a diverse, often-eccentric taste in workouts, too.
Nikki Metzger is Women's Health's 2015 Next Fitness Star winner and the creator of the heart-pumping, cal-torching method you'll find in her Ignite routine. You already know that a regular old bodyweight