Outside of having stellar genetics and/or the metabolism of a teenager, there’s generally one thing that separates those who have good abs and those who don’t: a good diet. Most people eat too much to ever uncover a six-pack. That’s the nutrition side of things.
As for training, let’s first dispel the myth that the abs are some magical muscle group that’s unlike any other in the human body and need to be trained higher reps than the pecs and biceps. Every skeletal muscle in the human body responds the same way. You can, and should, train your abs in the 8-12-rep range to increase their size and help them show through.
Most everyone knows that spot reduction is a fallacy, yet people still think they can target each “cube” of their midsections. Truth is, our abs, while appearing separate and distinct, are really one long muscle, separated by horizontal bands of fascia that create the iconic "six-pack". You may feel like one section is working harder than another, but the entire muscle is being trained when you do crunches and leg raises. With proper form on your ab exercises, you’ll get maximum activation of the entire muscle, from sternum to waistline.
Heavy lifting forces abdominal muscles to work harder to stabilize the body, as does balance and core work, but to promote maximum six-pack development, you need to isolate the abs with high intensity. Keep your exercise reps in the hypertrophy range and work on increasing resistance, just like you would with a bench-pressing program.
In the workout below, a weight plate held against the chest can be added to decline bench and twisting crunches when bodyweight alone becomes too easy, and on knee raises, a medicine ball can be held between the knees. Before you add weight, however, make sure you can complete your sets doing each rep slow and under control.
Core Carving Routine
Exercise Sets/Reps Day 1 Day 2 Day 3
Hanging High Knee Raise* 4/8 3/12 4/8
Decline Bench Crunch* 3/8 4/12 4/12
Cable Crunch 4/8 3/12 4/8
Twisting Crunch* 3/8 4/12 4/12
Note: Perform this routine three days a week for four weeks, switching the order of exercises each workout. Rest 90-120 seconds between each set.
*When the prescribed rep count becomes too easy with bodyweight, add resistance in the form of a weight plate or medicine ball.