The Undisputed Best Ab Moves, According to Pilates Instructors

"By far, my favorite at-home Pilates ab exercises are variations of planks," says licensed Pilates instructor Lisa Kaye. "They work your entire body and core." She recommends the slow mountain climber, a move that targets your lower abs with a challenging in-plank crunch.

1. Start in a high plank with your shoulders over your wrists.
2. Bring your right knee forward toward your chest, pulling your abs to your spine to deepen the ab work, holding the position for two to three seconds.
3. Switch legs, returning your right leg to plank and pulling your left leg in toward your chest. That's one rep.