For anyone who has ever stepped foot in a gym, beautiful abs are at least a hopeful side-effect, if not the primary goal, of training. Because of this, abs are one of the most popular muscle groups to train, with countless exercises and equipment available to do so. But what is the best way to develop these often elusive muscles? Some basic fitness principles can point us in the right direction. First, let's go over a bit of basic anatomy.
Our abdominal wall is composed of 4 primary muscles. The Rectus Abdominis, our "six-pack muscle", is easiest to see and most often thought of when abs are discussed. The Internal and External Obliques, most commonly referred to as "side-abs", actually lie underneath the Rectus Abdominis and are important for sideways bending and rotation of the core. The Transverse Abdominis is a deep muscle we cannot see that primarily stabilizes the core. Though most of these muscles are responsible for flexing the trunk & spine (as in a crunch), their most important function is stabilization of the spine.
Our ability to improve our bodies and specifically develop our muscles depends on the amount of stress we use during training. Stress in training is a workout. The tougher the workout, the more improvement we can expect. But "tough" doesn't necessarily mean a person's opinion on their workout, but more objective measurements like weight. Resistance training is effective because we can use progressively heavier weight to strengthen and develop our bodies. This applies to every muscle group, including abs.
If the magnitude of training stress dictates the most effective methods, then are bodyweight crunches, twists, and leg-lifts the best way to develop our abs? The answer is no. If we want to effectively train our abs, we need to train their primary function of stabilization. In other words, we want exercises that prompt these muscles to isometrically contract to stabilize the spine. Which exercises best do this? Compound barbell movements. This is convenient, because these movements also allow us to fulfill another previously discussed training requirement.
When using movements like the squat & deadlift, our abs our asked to perform their basic function of stabilization. These exercises also allow us to use some of the heaviest amounts of weight in a training program. These large stresses allow us to train these muscles optimally, even though we aren't performing an "ab" exercise. Put another way, if you can squat and deadlift 400+ pounds, you must have strong and developed abdominal musculature.
The last topic we must address is the finishing touch to the six-pack aesthetic. The above strategy prompts maximal development of the musculature, but that doesn't guarantee a visible six-pack. The other step is body fat reduction. We cannot train to "spot reduce" body fat (100 crunches a day won't "melt" stomach fat). When we lose body fat, our body slims in, more or less, even proportions. Therefore, a focus on overall body composition change is needed. This change will be best accomplished with a nutritionally sound, personalized diet combined with a good training program.
The hopeful take-away from this post is that the ab aesthetic people seek comes from attending to general fitness practices. If you have a focused diet and train progressively with compound movements you will optimally develop the fitness and appearance of your abs. Hundreds of daily crunches and leg lifts are both unnecessary and generally ineffective. In short, eat well; train smart; train hard!