Among CrossFit’s many puke-inducing exercises, one that doesn’t seem like it should be all that difficult is the “double-under” (swinging the rope under your feet twice during one jump). If you haven’t picked up a jump rope since fifth grade, you have no idea how misguided that assumption is. Colorado, however, has a resident expert who can help: Louisville’s Molly Metz, a five-time jump roping world champion who once completed roughly 1,400 unbroken double-unders in 10 minutes and now provides nearly 150 double-under seminars a year through her JumpNRope business. The 42-year-old Colorado native fell in love with competitive jump roping when a touring team visited her Louisville elementary school.

Today, in addition to developing performance jump ropes—yes, there’s such a thing—she coaches her own competitive squad (Mad Hops). Next month, her trainees will test their skills at the AAU Junior Olympic Games in Des Moines, Iowa. Of course, the sport offers more rewards than just winning, Metz says. “Jumping rope is crazy good for your brain,” she says. “The separation between hands and feet when you start working on footwork patterns, double-unders, and speed work keeps the brain on its toes.” For those of us whose brains are more on their keisters, Metz offers this step-by-step guide to mastering the double-under.

Start sans rope

Begin by perfecting your single-under. Put on a metronome or song that’s 110 beats per minute. With every beat, jump and land on the balls of your feet. Tighten your core and keep your hips aligned over your knees and toes (this is called “triple extension”) with your shoulders loose and slightly forward. Relax your gaze, and keep it on the floor about three feet ahead of you.

Master hand position

With your elbows bent and your hands about five inches to the sides of your hip creases, stick your thumbs out 45 to 55 degrees from your centerline. When you jump, your thumbs should flick down as your body goes up. For the double-under, change the hand count: Every third jump, flick your thumbs down twice.

Grab a rope

Apply the same setup. Make sure your bounds are fundamentally good—don’t pull your knees up higher on the third jump. Your third jump should simply be the most explosive to give your hands time to “think” while maintaining your triple extension.