May 2 -- Runner's World calls sports bras the most important piece of apparel for women runners.
"You want to minimize bounce," said Deborah Compton, manufacturer's representative for Moving Comfort, a maker of sports bras and other women's fitness apparel. "Each breast can weigh as much as five pounds."
Breasts are held tight to the body with ligaments, called Cooper's ligaments. Once those ligaments are stretched, that can cause the breasts to begin to sag. "Once they go, they go," Ms. Compton said.
That's why a sports bra is a must for any woman jogging or becoming involved in any sport that involves movement. Women who run, ride horses or mountain bike need supportive bras that will be comfortable.
Proper fit: What to look for
A sports bra will fit more snugly than a lingerie bra, although it shouldn't be so snug it will restrict movement or breathing.
"You don't want chafing," Ms. Compton said. "You need to turn the bra inside out and check the seams. Flatter elastic is better than rounder."
Women planning to run in a marathon want to check for any seams that might rub. "Anything that feels abrasive, you want to watch for," she said. "It doesn't take much in a marathon."
The straps need to feel comfortable, and be in the right place, not digging into the shoulders. The bra shouldn't chafe around the armholes or ribcage. The band beneath the breasts should feel comfortable, but not binding.
"It's not an exact science," Ms. Compton said. There is a size formula. Wearing a lingerie bra, measure around the rib cage, right under the breasts. Add five inches to that size, and round to the nearest even number for the band size. For the cup size, measure loosely around the fullest part of the breast. Subtract band size from cup size. An A cup is one inch. The sizes go up, one inch per cup. DD is five inches, Ms. Compton said.
"More structure means more support," she said. "It's a good habit to turn a bra inside out, look at the finish seams and edges."
Women who wear A to C bras usually do fine with a compression sports bra, while larger-breasted women need sturdy cups that support each breast.
Tags should not stick into the bra, Ms. Compton said. "We use a silky label underneath the arm," she said. The back tag is heat-set into the bra.
There are a few seamless bras on the market, which work best for women who wear A or B cups.
Most sporting apparel manufacturers make sports bras out of synthetic, wicking material. That's the kind of material women should look for when shopping for a sports bra, she said. There is a problem inherent with sports bras, however, Ms. Compton said. Their compression does not allow for a lot of air flow, which means they get wet.
"They dry quickly once you stop, but they get wet," she said. "The bra is always the first thing I want to get off, because it's so snug."
Most sporting apparel manufacturers make sports bras for women, but it hasn't always been that way. More than 20 years ago, sports bras were unheard of. Ms. Compton said women would tie together two bras or wear an Ace bandage.
A couple of women athletes sewed together two athletic supporters, making the first sports bra for Champion. Examples of that first bra are now in the costume collections at the Smithsonian Institute and the Metropolitan Museum of Art.