By Michaela Ryan

Did you know there's no muscle in your breasts? Skin actually provides the main support. And there's also some support from fine, hair-like ligaments called Cooper's ligaments.

"The breasts are not very well supported for the amount of activity we want to do," says Deirdre McGhee, sports physiotherapist and lecturer in functional anatomy at the University of Wollongong.

Many women experience breast discomfort if they exercise in an unsupportive bra. It's more common for larger breasted women to experience this, however, it does happen to smaller breasted women as well.

A well-fitted sports bra significantly reduces this discomfort. That's because a sports bra limits the amount of breast movement by 50 percent compared to bare-breasted exercise and 30 percent when compared to a lace fashion bra, according to Deirdre's research.

Small boobs?

Smaller breasted women (A and B cups) often exercise in a crop-top style sports bra. These bras limit breast movement by compressing them. So it's no good to have a crop top with a plunging neckline — make sure the bra covers your boobs entirely.

When choosing a crop top, Deirdre says to look for a rigid elastic material. If it's as thin as a T-shirt, that won't give you enough support.

Larger boobs?

Larger breasted women need soft cup or underwire sports bras.

"The straps need to be firm enough that they don't slide off the shoulder, but not so tight that they're digging in," Deirdre says. "And the part of the band at the front that's between the breasts — that must be sitting on the breastbone."

Make sure the underwire sits on your ribs and breastbone, not the breast tissue. Some larger breasted women wear one of these bras underneath a crop top. This can reduce breast movement quite well, but it can also leave you feeling too hot.

Proper fitting

If you don't fit yourself properly, your bra probably won't do its job.

If your breasts bulge above the cup or crop top, the bra is too small. If there are wrinkles in the cup or crop top, then the bra is too big.

The band should fit around your trunk comfortably. If it's too tight it can restrict your breathing. And you'll know if it's too loose if it slides up and down your trunk as you move your arms up and down.

While you're in the fitting room, Deirdre suggests running on the spot to get an idea of how comfortable and supportive the bra will be.

What works for you

Some bra manufacturers point out the level of activity which is suitable for their bras. For low-impact exercise such as yoga, walking or road cycling, you'll probably be fine in a comfortable bra with basic support and breathable material (cotton breathes better than synthetics). For higher impact sports such as running, netball or mountain biking, again it's important to find a bra that's cool and comfortable, but strong support is more vital.

Through trial and error, work out which design suits your individual needs. If your sports bra is uncomfortable in any way, your performance will be affected. So it's worth shopping around until you get it right. Then you can forget all about your boobs and get on with the fun! Which is the point, after all.

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