The rectus abdominis receives all the credit for a well-developed midsection. But there's an underrated star beneath it that can pull your stomach in and enhance your six-pack even more!
When you think of your abs, you envision the six-pack. You imagine the perfectly carved rectus abdominis muscle that's ever so visible, at least if your body fat is in single digits.
You hardly ever consider other muscles of the midsection. But today, I want to familiarize you with the transverse abdominis. It's actually located behind the rectus abdominis and isn't visible—but that doesn't mean you should skip training it. Training the transverse abdominis can effectively help you develop a better six-pack (yes, that's right) and even strengthen your core.
First, it's useful to understand how the transverse abdominis works. Bear with me as I wade into a little bit of science.
What Is The Transverse Abdominis?
The transverse abdominis (TVA) is the deepest layer of muscle tissue in the abdominal wall. It originates from the costal cartilage of your lower six ribs, the anterior portion of the iliac crest (the top part of your hip bone) and the inguinal ligament. It wraps around to the front where it connects to what's called the xiphoid process (the base of your sternum), pubic tubercle (front of pubic bone), and linea alba (which separates the right and left halves of your six-pack).
The primary purpose of the often underrated transverse abdominis is to compress the abdomen; the secondary purpose is spinal and core stability.1 This may not sound like much at first, but it essentially means that without the transverse abdominis, you wouldn't be able to hold your stomach in, and it would appear distended. In layman's terms, you'd be rocking a beer belly.
You're probably familiar with a "vacuum" or possibly the "vacuum pose" that was popularized by one of Arnold Schwarzenegger's bodybuilding rivals, Frank Zane. What this actually refers to is one's ability to contract the transverse abdominis (basically, sucking in your stomach). This is ideal from an aesthetic standpoint, as you can simultaneously contract (or flex) the transverse abdominis at the same time as the rectus abdominis to create a bit more of a dramatic look to the abs overall.
Imagine flexing your abs while your stomach is protruding—it wouldn't look too impressive, right? You may still see the overall outline of your six-pack if you're lean enough, but imagine how much better your abs would appear if you were able to simultaneously "suck in" your entire stomach at the same time. By training the TVA, you're essentially building up your endurance at holding your stomach in, which is something that can be quite difficult to do over longer periods of time, like standing on stage or posing for a photo shoot. Heck, it even helps when you want to look your best at the beach!
Because of muscle-fiber make-up, strengthening the transverse abdominis is more oriented toward endurance-style training than the methods you'd use to target most skeletal muscle groups. Think of holding plank exercises for a period of time. Those muscle aren't going to grow much as a result of those exercises.
Based off the mechanics of the muscle, most of the strengthening of the TVA comes from compound movements that require full core and lower-back stabilization—think squats and deadlifts. A stronger TVA acts as nature's weight belt, stabilizing the spine and pelvis during lifting motions. Ironically, if you're always wearing a weight belt, you may unknowingly be weakening the muscle.
Doing specific rectus-abdominis movements like crunches and hanging leg raises alone does have some tangential effect strengthening the TVA, but they're not enough to pull your belly in. Here, doing exercises to effectively strengthen the TVA are essential to improving your vacuum while helping to reduce abdominal protrusion, not to mention the positive effect that may have on your lower back.
Dedicated TVA Exercises
There are three simple exercises that effectively target the transverse abdominis: vacuums, plank vacuums, and Swiss-ball roll-outs.
When performing these movements, focus on the compression of the abdomen. Since that's the natural function of the TVA, it's important to focus on emphasizing the compression of your abdomen in order to maximally tax the TVA and increase its strength.
Stand and suck in your stomach, focusing on drawing your belly button back into your spine. It may be difficult at first, but after a few times through, you'll be able to draw in your abdomen and perform a solid vacuum.
2. Plank Vacuum
The plank vacuum is essentially the same motion as a traditional vacuum, except you're in a plank position on the floor (which is basically the top of a push-up). You'll follow the same protocol as above, but being prone forces you to work directly against gravity, thus making it a more advanced variation.
3. Swiss-Ball Roll-Out
Place your shins on an exercise ball with your hands on the floor. Roll the ball toward your chest by driving your knees into your chest, flexing your abs in the process. Ordinarily, this would just be a normal exercise for the lower rectus abdominis, but if you simultaneously focus on drawing in your gut and performing a subtle vacuum at the end of the movement (when the legs are extended), you'll notice a much stronger engagement of the abs. This is a great introduction to how improving the TVA can begin to help you train your rectus abdominis (the six-pack) more effectively.
The best thing to do, in my opinion, is to train the transverse abdominis three times per week. Do it after your weight workouts, when you're already slightly fatigued. This does not replace your normal ab training; it should be an ancillary set of exercises that'll enhance your six-pack like never before!