It is common knowledge that the 'abs' are the visual centerpiece of any muscular physique. In bodybuilding, modeling, or simply looking great, a chiseled six-pack is an absolute must. Without a ripped midsection, you won't go far. Arguably however, the most important function of the abdominal region is to provide a strong and functional core on which both the upper and lower body move. Weak core muscles can lead to decreased sport performance, poor posture, and low back pain. Now that we've established how important a well-developed set of abs is, let's get into the nuts and bolts of abdominal training.
When someone mentions abs, most people immediately think of the rectus abdominus muscle. This is the muscle that is responsible for the six-pack appearance. The rectus abdominus muscle runs from the bottom of the rib cage and the xiphoid process to the pelvic brim and the pubic symphysis. When this muscle contracts (shortens) it brings the lower front part of the rib cage closer to the front part of the pelvis. This is also called spinal flexion due to the fact that when this motion occurs, the lumbar and thoracic (lower and middle back) regions of the spine are flexed forward. This muscle can be trained by doing crunches, Swiss ball crunches, rope crunches, or reverse crunches.
Another muscle of the midsection is the oblique muscles. These muscles lie to the side of the rectus abdominus muscle and wrap around the sides of the waist. There are two sets of oblique muscles: the external obliques (which are visible on someone who is very lean) and the internal obliques (which are not visible). The function of these muscles is to aid the rectus abdominus in spinal flexion and to rotate the trunk and spine. The obliques can be trained by performing any of the above crunches with a twist, trunk rotation, or side bend.
Last, but definitely not least, and located in the midsection musculature, is the transverse abdominus (TVA) muscle. The TVA runs sideways across the body under both the rectus abdominus and both of the oblique muscles. It is the only one of the abdominal muscles that does not cause movement of the spine. The function of the TVA is to pull the abdomen in and compress the internal viscera. In other words when the TVA contracts, the circumference of the midsection decreases and the navel gets closer to the spine.
A perfect example of this is the vacuum pose that was made famous by Frank Zane. As you can probably imagine, bodybuilders who have a shredded but distended midsection suffer from a weak transverse abdominus muscle. To train the TVA, begin by exhaling completely, then pull your navel as close to your spine as possible. Hold for 10 – 20 seconds (don't pass out!) In addition to this exercise, keep your abs tight and slightly pulled in all day long. You thought sucking your gut in was cheating! It's not.. It's a valid exercise.
Some people believe that the abs should be trained every day. Others say they should be trained only as often as the other muscle groups (one to two times per week). My recommendation is somewhere in between what I consider to be two extremes. Training them everyday would likely lead to over training. However, I do believe the abs can recover faster than other muscles like chest, back, and legs. Therefore they should be trained more often than these muscles. As a general rule, wait about 48 hours between abdominal workouts.
An exception to this is the transverse abdominus. The goal of training the TVA is not to cause it to hypertrophy (growth), but rather, to improve the neuromuscular efficiency of the muscle. In English, that means to "tone" the muscle. To achieve this, the muscle should be trained multiple times per day, every day. Try training the TVA with the vacuum exercise three times per day: upon wakening, midday, and before bed.
When planning your ab workout you should select one or two exercises for each muscle group. Generally, I would probably recommend two exercises for the rectus abdominus and one for the obliques. Each exercise should consist of about three sets each.
But before you head to the gym to put this stuff to work, let's dispel some myths about abdominal training. First of all, there is no such thing as spot reduction. Doing side bends and twists will NOT get rid of you love handles. Dieting and doing cardio will. Think of it this way, when you put on fat you do not get to select where on the body it will ultimately reside (unfortunately). Likewise, you can't select from where it will come off. Fat will be lost in the reverse order that it was put on. You've seen people in the gym that train abs like there's no tomorrow, eat whatever they want, and do no cardio. Yet, somehow, they expect their efforts to yield the much wanted "six-pack" look. It's quite possible the underlying musculature is well enough defined; but it's not visual because it's covered up with fat. So keep in mind that developing the midsection you want is a two-step process, developing the muscles and losing the fat on top of them.
Secondly, hanging leg raises and leg lifts are excellent exercises for the hip flexor muscles, not the abdominals. Training the hip flexors too much, especially without adequate stretching, can lead to a shortening of the iliopsoas (hip flexor) which can cause an increased curve in the lumbar spine (hyperlordosis) and lead to low back pain.
When you begin with your legs straight down and pull them up to 90 degrees, that movement is called hip flexion. Makes sense that the hip flexors would do that movement, huh? Your abdominal muscles only contract isometrically when you do these movements. Your abs also contract isometrically when you have a bowel movement, but this is obviously not the best way to train them. An isometric contraction means there is no lengthening and shortening of the muscle.
A muscle must be trained through its full range of motion for maximum benefit. However, if you started with your legs at 90 degrees of hip flexion and pulled your pelvis toward your sternum, the rectus abdominus would contract. This movement performed on the ground is called a reverse crunch. The same movement performed while hanging is called very difficult. Not too many people can do it from a hanging position. Give it a try!
Now that you have a basic understanding of the anatomy, biomechanics, and recuperative ability of the abdominal musculature, go make it happen.