Reverse Crunch Reps: 15 Lie on your back on the floor. Place your hands on the floor beside you. Bring the knees in toward the chest with your feet together. Use your abs to slowly curl your hips off the floor and into your chest, and then slowly lower them back to the starting position to complete one. Don't swing your legs to create momentum; use your abs to control your movement. Do 15 reps. Image Source: POPSUGAR Photography