The abdominal muscles, often referred to as the “abs”, are composed of several distinct muscle groups. When people talk about wanting a “six-pack,” they’re typically referring to the rectus abdominis muscle. This muscle runs vertically down the front of the abdomen and, when well-defined, can produce the coveted six-pack appearance. The six-pack is actually made up of three pairs of muscular segments on the rectus abdominis, and how they appear is largely determined by genetics, body fat percentage, and muscle development.
However, not everyone has a three-pair, or six-segment, configuration. Some people may naturally have an eight-pack, while others might have a four-pack. The four-pack configuration, where there are only two visible pairs of muscular segments, is the rarest of the common configurations. Even with low body fat and well-developed muscles, if someone is genetically predisposed to have a four-pack, that’s what they’ll display. This doesn’t mean their abs are any less strong or functional; it’s simply a matter of genetic variation in muscle structure.
The external obliques, which are located on the sides of the abdomen, and the transverse abdominis, which is the deepest abdominal muscle that wraps around the torso, are other crucial parts of the abdominal muscle group. However, these muscles don’t contribute to the “pack” look in the same way the rectus abdominis does.
While the six-pack configuration of the rectus abdominis is the most commonly desired and recognized, the four-pack configuration is the rarest. Regardless of the number of segments, the key to visible definition is a combination of muscle development and a low enough body fat percentage to reveal those muscles.