Popsugar Health & Fitness Workouts Best Crunch Variations Add These 20 Crunch Variations to Your Routine and Chiseled Abs Are on Their Way! 5 August 2018 by Jenny Sugar View On One Page Photo 8 of 20 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 8 Straight-Leg Sit-Up Begin on your back with your legs straight and arms raised toward the ceiling. Roll up to sitting, focusing on the abs rounding the back. Roll back down to the mat slowly, one vertebra at a time. This completes one rep. Previous Next Start Slideshow WorkoutsAb Exercises