WORKOUT FOR SIZE
Low body fat may help your waistline appear lean, but that doesn't mean your abs have the peaks and valleys to make your midsection pop. Here's a routine that uses added resistance beyond your body weight to signal muscle growth, helping transform a merely flat or underdeveloped washboard into a three-dimensional, topographical six-pack. The workout is also balanced between the three key areas of the midsection—the upper abs, lower abs, and the obliques—to ensure top-to-bottom, side-to-side development.
To thicken up the bricks of the rectus abdominis (six-pack), you'll choose a resistance so that you reach muscle failure at a fairly low rep target, about 8-12. This relatively heavier weight is superior for building muscle compared to high-rep bodyweight exercises. Similarly, if you want to build thicker obliques, continue to use a fairly low rep target. Many lifters aren't looking to build a blockier midsection, so they instead choose slightly lighter weights on oblique movements.