Expert Q&A

Ab exercises: Can resistance training make your abs bulky?

Is it true that adding resistance to abdominal training will make my abs bulky?

What exactly are your 'abs'?

To answer this question, let’s start with a short anatomy lesson. What we think of as our ‘abs’ is actually a thin sheet of muscle known as the rectus abdominis. The top of the sheet attaches to the breastbone; the bottom of the sheet attaches to the pubic bone. The rectus abdominis is separated down the middle by the linea alba, and by attachments of connective tissue running crosswise, which provide the ‘cuts’ that make up a ‘six-pack.’ Think about those bumps on underwear models’ bellies—they aren’t a bunch of little abdominal muscles, they’re connective tissue attachments that act like ropes pinning down a tent. These ‘ropes’ help provide the characteristic ridges and valleys of the muscle’s shape. 

You middle is not just muscle - but also internal organs and body fat

The rectus abdominis isn’t the only muscle on the midsection. It’s layered with other muscles such as the internal and external obliques, and the transversus abdominis. The rectus itself is quite thin; it is approximately as thick as the average magazine. Many people are convinced that midsection girth can be attributed to big ab muscles. In fact, most of the midsection is composed of either internal organs or body fat. If you look at a torso in cross-section, you’ll see that the abdominal girdle is just a thin ring of muscle surrounding a body cavity full of other squashy stuff, and that these thin muscles themselves are encircled by what is in the average North American a substantial layer of fat. 

The fat around your middle: is it visceral or subcutaneous?

Speaking of fat, it’s worth mentioning that there are two types in the midsection: visceral fat (which cushions the internal organs) and subcutaneous fat (which sits under the skin—it’s the stuff you can pinch if you grab a hunk of tummy). Most men put on more fat around their waists (known as the ‘apple' shape’), while the majority of women tend to put on more fat around their lower bodies (known as the ‘pear shape’). As both sexes grow older, they both put on more fat around their internal organs. 

Often bulky waistlines are due to fat, not muscle

In other words, most of the time what makes waistlines bulky isn’t muscle, it’s fat. You could train your abs with Herculean effort and the ability of those muscles to get larger would still be dwarfed by the ability of the body to store fat in that area. So if you want a slim waist, go ahead and add some weight to those crunches…and remove that weight from your fork.

Krista Scott-Dixon, PhD
Contributing Expert

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