Hip thrust

Use your abs to lift your hips off the mat only a few inches, pushing your heels toward the ceiling. Can also be done on an incline board to increase the level of difficulty.

Crunch

Lie on the floor with your knees bent at about 60 degrees, feet flat on the floor about shoulder-width apart. With your hands lightly gripped behind your head (not pulling), curl forward to bring your shoulders blades just off the floor.

Back Extension

Lie facedown on a back-extension bench with your heels under the pad. With your body straight, head neither flexed forward nor extended backward, and your arms crossed over your chest, lower your torso so your body forms an angle that approaches about 90 degrees. Use a smooth motion to rise back up to the starting position.