Lie on your back with your arms along your sides and raise your legs, knees bent at roughly 90 degrees. Curl your knees in toward your chest, lifting your hips and lower back off the floor as your feet point up toward the ceiling. Lower back down with control until your hips return to the floor, without letting your feet touch down between reps. The lift comes from curling your pelvis up, not from swinging your legs - momentum is the enemy here.

Works: abs, obliques, hip flexors

Breathing: Exhale as you curl your knees in and lift your hips, inhale as you lower back down.

Common Mistakes: Swinging the legs to generate momentum, pressing hard into the floor with the hands to lever the hips up, and dropping the hips back down instead of lowering them under control.

Make Easier: Lift only until your lower back leaves the floor without raising the hips high, or build up with regular Crunches first.

Make Harder: Lower your legs with a slow 3-count on every rep, or progress to Butt-Ups to do the same lift with straight vertical legs.