Ab Crunches

Lie on your back on the floor with your knees bent and feet flat. Put your hands to the sides of your head and tuck your chin forward. Slowly raise your upper back off the floor, squeezing your abs and pulling your chest toward your thighs as you exhale. Pause at the top of the movement, then slowly lower as you inhale but do NOT lay your head back. Keep your hands and arms fixed throughout.

   Ab reverse crunches

Lie on your back on the floor with your hands holding a weight (like a medicine ball) on the floor just above your head for stability. Keep your knees bent and your feet off the floor near your butt. This is the starting position. Flatten your lower back to the floor and raise your knees toward your elbows, bringing them as close as you can without allowing your upper back to round. Return to the starting position. That's one rep.

   Ab Bent-knee V-ups

Lie on your back with your hands above your chest and your feet off the floor with your knees slightly bent. Keep your head forward. This is the starting position. Slowly raise your back off the floor while simultaneously drawing your knees toward your chest, then return to the starting position only until your middle back just touches the floor. Use a smooth motion throughout. Avoid throwing your arms forward--keep them in a fixed position.