Here's what you need to know...

Ab workouts should be simple, quick, and effective. In fact, you only need two exercises and perhaps a third to work the "vacuum." The biggest error people make in training abs is their breathing. You need to inhale deeply before executing the movement and then as you crunch or leg raise, blow all of your air out. This forces your abs to contract.

A lot of people ask me why I don't write more ab routines. The truth is, I assumed people would find my suggestions too simple. But an ab workout should be simple, and quick, and effective. In fact, you only need two exercises and maybe on occasion a third to get what you want out of your abs.

Only Two Exercises

The first exercise is primarily a "lower ab" movement where you bring your pelvic girdle toward your torso. For me, that means leg raises. There are three primary versions I use:

Hanging from a bar. Keep your legs straight and form an L shape (don't bend the knees) in the contracted position. Done upright on a stand where you can rest your elbows. Lift your legs until they're parallel to the floor. Don't swing the legs. Make sure your legs don't fall so low that you lose the tension in your abs and you have to use your lower back muscles. Lying on a decline bench so that your head is up top and feet are closer to floor. Use a rope (the kind you use for doing triceps pushdowns) looped around the bench and hang onto it while lifting the legs towards the head. You can get really aggressive on these and do them with perfectly straight legs, Rocky Balboa style!

Rep ranges

These are going to vary wildly. I like to do 20-25, but 10 reps might be enough if you do them with perfect technique. Just do as many as you can with perfect form and then stop. Build your reps through intelligent progression. Chances are if you can do 25-plus reps, you probably don't even need to read this article and you're an ab-training badass.

The second exercise is primarily an upper ab movement in which you take your torso to your pelvic girdle. Here are the three main options I use:

Incline sit-ups These are the classic Roman chair sit-ups. Rope crunches These are great and hugely effective, but you have to work on finding the exact weight and knee placement, so they do take a bit of practice. Band crunches I find these to be very effective as well. I learned this one from my powerlifting brothers and sisters. You'll again have to experiment to find which band works best for you.

Rep ranges

These exercise variations typically allow for higher reps. Shoot for 25-30 on each of these. If you can't do that many, just gradually work your reps up using perfect form.

The third exercise is optional and it's for building a vacuumed waist:

Pulldown crunches

Seat yourself in a pulldown station and grab the bar overhead as if you were going to do pulldowns. Now inhale very deeply and suck in your stomach as hard as you can. Try to push your abs against your spine. Next, blow all your air out as you crunch down. These are excellent for gaining control of your abs and for those who suffer from abdominal distention.

Here's a client of mine that does these often and you can see how vacuumed her stomach is.

The Combination Move

Here's an option. I sometimes combine an upper and lower ab movement by doing V-Ups. I'll just do 4 sets of 10-15 reps twice a week and that'll be it for my ab workout. Done.

Additional Ab Wisdom

If I had to pinpoint the biggest error people make in training abs, I'd say it's their breathing. You need to inhale deeply before executing the movement and then as you crunch or leg raise, you blow all your air out. This forces your abs to contract.

Another tip you might find useful is to use equipment that allows you to stretch out your abdominal wall and get more range of motion. So if there's a machine or tool that allows you to get this extra stretch, use it. For instance, we slap a BOSU ball onto the back of a hanging leg raise and it gives us increased range of motion.