Reverse Crunch

A good exercise for developing the lower abdominal muscles, if performed correctly. Avoid this exercise if you have lower back pain.

Lie on your back, keeping your hands by your sides, and your head firmly on the floor, looking up towards the ceiling.

Lift both legs up, aiming to bring your feet vertically in-line with your pelvis, legs straight. If you have weak abdominal's or poor flexibility you may have to bend your legs, however try and keep your thighs vertical (knees above your pelvis).

Slowly contract your lower abs, aiming to push your pelvis and lower back 1 - 2 inches off the floor, taking your feet vertically upwards.

Avoid any swinging of legs forward and back, as this momentum is what lifts the back and reduces the benefits of the exercise. Crossing the legs aids in stability, and as such makes the exercise easier.

Don't be disillusioned if you're unable to come off the floor, this exercise if performed correctly is difficulty, however the contracting action will develop lower abdominal strength.
 

Even though a difficult exercise, beginners should aim for 6 - 10 lifts / contractions, however never force the movement.

Intermediates aim for 10 - 15 reps repeated twice with 20 - 30 seconds rest.

Advanced work for 20 reps+ repeated twice, with 20 seconds rest.

For maximal abdominal benefit, use your arms just for stability; avoid pushing down on your hands in order to push yourself up.