Working behind a computer all day has serious health implications. Here are some exercises to keep your abs in fine form.
Allabs
Laying face-down with arms extended above the head, lift chest and lower rib cage off floor. You may wish to have a partner hold down your feet. (Beginners: 10-15 reps. Intermediate: 20-30 reps. Advanced: 50+ reps.)
Belly-Ups
Laying face-up with hands on the belly, lift shoulders and lower back off floor. (Beginners: 10 reps. Intermediate: 50 reps. Advanced: 100+ reps.)
Crunches
Laying face-up, with bent knees, ankles crossed and feet off the floor, place hands behind the head and lift chest toward thighs. (Beginners: 10 reps. Intermediate: 50 reps. Advanced: 100+ reps.)
Double-Leg Pikes
Laying face-up with arms extended above the head, simultaneously lift arms, torso and both legs. Reach for toes while keeping legs straight. (Beginners: 5-10 reps. Intermediate: 15-20 reps. Advanced: 25-50 reps.)
Single-Leg Pikes
Just like “Double-Leg Pikes,” but lift one leg at a time, alternating. (Beginners: 10 reps. Intermediate: 25 reps. Advanced: 50+ reps.)
Bicycles
Laying face-up with knees bent and feet on the floor, clasp hands behind head and move legs in pedalling motion (alternating) while twisting the body so the leading elbow meets the opposite knee (and repeat, rotating). (Beginners: 25 rotations. Intermediate: 50 rotations. Advanced: 100+ rotations.)
Standard Leg-Lifts
Laying face-up with legs together and arms at the sides, raise legs together (four inches off the floor) and hold for 15 seconds. (Beginners: five reps. Intermediate: 10 reps. Advanced: 25+ reps.)
Hell Raisers
Laying on side, legs together, bottom arm extended on floor, place upper hand behind the head, raise and bend legs, and crunch (touching the upper elbow to the upper knee). Make sure to keep legs off the floor at all points. (Beginners: 10-15 reps./side. Intermediate: 20-30 reps./side. Advanced: 30-40 reps./side.)
Chucks
Laying face-up with knees bent and feet on the floor, cross-over one leg so the ankle rests on the opposite knee. Place hands behind head and lift back while twisting (the leading elbow should meet the opposite knee.) (Beginners: 10 reps./side. Intermediate: 25 reps./side. Advanced: 50+ reps./side.)
Supermans
Laying face-down with legs together and arms extended above the head raise arms and legs, holding for 15 seconds. (Beginners: five reps. Intermediate: 10 reps. Advanced: 25+ reps.)
Row-Boats
In a seated position, with bent legs raised slightly and arms crossed over chest, lean back (resting only on the buttocks) while straightening legs and body. Return to starting position and continue. The movement should be similar to rowing. (Beginners: 5-10 reps. Intermediate: 15-20 reps. Advanced: 30-40 reps.)
Scissors
Laying face-up with arms at the sides, lift legs slightly off the ground and begin a rapid, alternating motion of separating and crossing the legs. (Beginners: 10 reps. Intermediate: 25 reps. Advanced: 50+ reps.)
Thrusters
Resting on upper back and shoulders, with legs raised and arms extended on the floor (to brace body), thrust both legs straight up, and release. (Beginners: 10 reps. Intermediate: 25 reps. Advanced: 50+ reps.)
(from Swim Magazine – http://www.swiminfo.com/articles/swimmagazine/articles/199505-02swim_art.asp)