Photo by Athleta, Champion and Moving Comfort

Designers are bettering the sports bra through comfort construction and new fabrics, and by evolving the classic style. Three innovative options are (from left) Athleta Sprint Seamless Bra Top, with a style that offers smaller-chested women more shape ($45); Champion Double Dry Spot Comfort with gel-cushioned straps that don’t dig into shoulders and a padded hook-and-eye closure ($40); Moving Comfort Juno with cups that are lined with S.Cafe fabric, which is made from recycled coffee grounds and helps eliminate odor and wicks away sweat ($52).

Everyone has a pair of feet, but women have an additional pair of something to worry about while exercising. And they're every bit as tricky to fit, control and protect, which is why bras are beginning to rival shoes as the most technical of all sporting apparel.

When the Jogbra was born in 1977, two jockstraps stitched together were a revelation. These days, the science that goes into corralling women's chests is much more extensive, with garments designed to smush in and hold up while wicking moisture, feeling comfortable and, hopefully, looking good.

The best news is for well-endowed women. More designers have jumped into the market with gravity-fighting creations, including Athleta, which launched its Signature Sports Bra line in January. The Va Va Sport Bra Top ($54) runs up to size 38DD and is the Gap Inc. brand's No. 1 seller. And good luck trying to track down Lululemon's newest bra, the Bust Stops Here ($58), which promises maximum support and coverage. It's sold out online.

Most bras address vertical movement but fail to control the breasts when they shift in other directions. "Different types of activity really require quite different support," says Joanna Scurr, head of the Research Group in Breast Health at the University of Portsmouth in Britain. "In tennis, there's a lot of upper body rotation, which leads to side-to-side breast movement. In basketball, it's more vertical." Scurr's research into the effects of breast support on athletic performance has led to the sport-specific line of bras ($68 each at www.figleaves.com) from Shock Absorber. The Run Bra zeros in on figure-8 movement, the Ball Bra has extra support at the top to control up-down bounce, and the Racket Bra is constructed in an M-shape to prevent too much lateral swing.

Just as running stores have systems for fitting shoes, similar strategies are getting more common for sports bras. Moving Comfort, a leading brand that was founded in the District of Columbia (but is now based in the other Washington), has made a huge push for proper sizing. Last month it distributed a step-by-step guide to 600 retailers nationwide. The guide includes a DialedFit Wheel to match measurements with bra size and a list of troubleshooting suggestions. (Uneven breasts? Fit to the larger one, then adjust the other strap and add a removable cup to the smaller one.)

Getting a good fit

Straps: If they're digging in or falling off, something's wrong. Keep in mind that racerback styles can't slip.

Cup: Measure around the fullest point of the bust and then subtract the rib cage measurement to determine your cup size. Many women opt for a too-large band and compensate with a too-small cup.

Band: Measure the rib cage just under the bust, then add four to get your band size. This should feel more snug than a lingerie bra and fit on the loosest hook.

Underwire: Some women refuse to wear underwire for exercise, but it makes the band more secure, which is especially helpful for those with larger chests.

Style: Compression bras hug the breasts to the body, while encapsulation bras support each breast separately. The best bets are combos that do both.

Shopping smart

1. Do your chosen activity when you're trying on a bra: run, jump, do downward-facing dog. "Try lying on your back," advises exercise scientist LaJean Lawson, who tests bras for Champion. "You don't want anything poking you."

2. Check out the side view. If your breasts are popping out, the cups are too small. If the fabric is wrinkling, they're too big. The band should stay level, and there should be no itchy or hot spots.

3. Repeat this process for your bras at home. The general rule: A sports bra should never celebrate a birthday, though that depends on how much it's worn and how it's treated.