The Complete Guide to Your Abs Muscles

Do you know every type of abs muscle in your core? This anatomy lesson can help you properly target and strengthen your abs.

If you're getting tired of doing endless crunches and seeing no results, then it might help to learn the ins and outs of your core anatomy and the science behind building muscle. For one thing, your abs aren't just one muscle — and you'll need to diversify your exercise routine to work every type of abs muscle and really see results.

Here, get to know each type of abs muscle, plus how to work them in the most effective ways. (BTW, core strength is about so much more than just having a six-pack.)

Meet Your Abs Muscles

First, a little anatomy lesson. Along with muscles in the lower back, these key abdominals make up your core:

  • External Obliques: The outer layer of the abs on your sides; these run diagonally downward.
  • Internal Obliques: Just underneath the external obliques, these run diagonally up your sides.
  • Rectus Abdominis: Two paired sheets of muscle from the ribs to the pelvis that flex you forward. (These are the ″six-pack" muscles most people visualize when thinking about the abs.)
  • Transversus Abdominis: The deepest muscle of the abs, which wraps around the waist to support the spine.
anatomy diagram showing every type of abs muscle
Alan Gesek/Stocktrek Images/Getty Images

Yes, there are separate muscles, but they all work together. The external obliques are the V-shaped muscles running diagonally down your sides that, along with the internal obliques underneath them, help you rotate your spine. The rectus abdominis, meanwhile, is the straight-down-the-center muscle which, yes, can make you appear to have a six-pack. The one remaining type of abs muscle is the transversus abdominis: The deepest-down of all, it does a complete wraparound of your midsection and pulls it in like a corset.

And while everyone has the same muscles, their appearance differs from person to person. The shape of your midsection boils down to a formula that includes factors such as body type, fat composition, and possibly even the shape of the pelvic bone, where your abs muscles attach, says Carrie McCulloch, M.D., a musculoskeletal anatomy expert and the medical director for Kinected Pilates studio in New York City. Some people build muscle more easily than others, and everyone's waist shape is different. That means that, theoretically, a wider pelvis can translate into a broad lower abdomen and hips, compared to what's above the belly button. "These are all variations on normal, and genetics can play a big role," says McCulloch.

What Determines the Visibility of Your Abs Muscles?

Think of your abs muscles as the meat in the middle of a fat sandwich: On top of them is subcutaneous fat, the stuff you can potentially see from the outside, depending on your body composition. Below them is visceral fat, which is the type that takes up residence next to your internal organs, which is protective in small amounts, but can lead to health consequences when too much builds up.

"When you fill up those subcutaneous areas, fat winds up getting stored where it shouldn't: in your deep abdomen or your liver," explains Arthur Weltman, Ph.D., an exercise physiology professor at the University of Virginia in Charlottesville. Visceral fat has been linked to heart disease, type 2 diabetes, and metabolic syndrome, he notes. It's impossible to know how much visceral fat you have just by looking in the mirror, so seeing a doctor is the only surefire way to find out if you have too much. However, factors such as your Body Mass Index (BMI) and your waist circumference can help you determine if you may be at a health risk.

You can also implement these strategies to help reduce visceral fat:

Limit Trans Fats

Step one to combat visceral fat is to toss the trans fats, which used to be found in prepackaged treats under the alias "partially hydrogenated oils." These are being phased out and are mostly absent from supermarket shelves since scientists discovered how unhealthy they are for your organs and beyond. (The World Health Organization aims to eliminate artificial trans fats worldwide by 2023.)

Instead of trans fat, seek out more monounsaturated fats, found in foods such as olive oil and avocado, and polyunsaturated fats, found in foods such as walnuts and salmon. These fats can help reduce your risk of cardiovascular disease, according to the Food and Drug Administration. (More: The Expert-Approved Guide to Good Fats vs. Bad Fats)

Get More Exercise

High-intensity aerobic exercise is even more effective at burning off visceral fat than the same amount of low-intensity exercise, notes Weltman. In one of his own studies, he had overweight women walk or jog five times a week; one group worked out for a longer amount of time at a low intensity, while the other did shorter stints of high-intensity work. Even though each group burned the exact same number of calories in each workout, the high-intensity group lost more visceral fat. "We speculate that there's a relation between the intensity of the workout and the amount of growth hormone released, which is a powerful mobilizer of visceral fat," explains Weltman.

The good news is that high intensity — the level at which you feel the effort and can no longer hold a conversation — is different for each person, according to Weltman. "You may have to run to get to that level, while someone else may just have to jog or walk," he explains. "It all depends on your level of fitness, but the great thing is, you can do it whether you're a competitive athlete or just starting out," adds Weltman. (P.S. This is the simplest way to gauge the intensity of your workout at any point.)

Does the thought of strapping on your running shoes fill you with dread? Well, lifting weights has also been shown to reduce visceral fat (as well as these other health and fitness benefits). A study from the University of Alabama at Birmingham found that subjects who strength trained lost more visceral fat than participants who just did cardio. Plus, they kept that visceral fat off after a year if they kept up the weight training, even if they gained weight overall.

The most important factor to consider? When choosing which type of exercise to do, prioritize what you like to do and feel motivated to keep up.

How to Build Stronger Abs Muscles

If you want visible, defined abs, losing weight is not a prerequisite — just work on toning the muscles, says Michele Olson, Ph.D., senior clinical professor of exercise physiology at Huntingdon College in Montgomery, Alabama. To build up your core strength, it's important to work every type of abs muscle in your body (instead of, say, just focusing on the rectus abdominis). And, turns out, the abs are pretty hard to fatigue because they work all day long to keep you upright.

But you don't come home after a long day at the office with a sore core from sitting at your desk, so how busy could they really be? "When you're seated, your back muscles and spine help keep you upright and the abs are in a slack position, especially if you slouch," explains Joseph Herrera, D.O., a doctor of osteopathic medicine and the director of sports medicine at Mount Sinai School of Medicine's Department of Rehabilitation Medicine in New York City. "Although you would end up reclining without the opposing muscle forces they provide, intentionally contracting your abs is the only way to activate them as you sit," he notes.

So how do you wake up those deep abs muscles if you're working at a desk all day? In a standard chair, your core muscles need not pull their own weight. But sit on a pumped-up stability ball (with no backrest) and the rectus abdominis activates to support your spine. "The stability ball requires your torso to balance on an unsteady surface. It forces your abs to fire," says Dr. Herrera. (You can also do these advanced core exercises with the help of a stability ball.)

In addition, you can activate the rectus abdominis and obliques by simply pulling in your belly button. To get functional benefits from your core workouts, you'll want to prioritize movements that activate more than one type of abs muscle. Previously, there was a tendency to isolate the abs muscles to give each one an individual workout (crunches for your rectus abdominis, bicycles for the obliques, and so on), but that's not the way it works in real life, notes Olson.

"When you're reaching up to get something, picking up a baby, or bending down, you need all the muscles to work together," explains Olson. "Instead of targeting each one, you should aim for functional fitness, where the muscles work as a unit," she recommends. (This hardcore abs workout is full of exercises that target multiple core muscles.)

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