What are some exercises for the lower abdomen?

Lower Ab. Exercises: Exercises -90 degrees static press, single-leg stretches, U-boat exercises, frog presses and leg lifts involve flexing the thighs and bending the knees at 90 degrees towards the chest, using abdominal muscles to lift legs. Leg- and hip-lift exercises, done while lying flat on the back and using the arms for support, pull in the abdominal muscles. See a Gym instructor to help for good Health.