Wearing the wrong bra, Ronda Rousey nearly flashed an entire arena in her February fight against Liz Carmouche. Jeff Gross/Getty Images

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MINUTES AFTER Ronda Rousey bounded into the Octagon this past February for the first women's fight in UFC history, she found herself grappling with two formidable opponents. The first was former Marine Liz Carmouche, who was suddenly suctioned to Rousey's back, strangling her and twisting her head. The second was her low-cut black crop top, whose elastic spaghetti straps were no match for Carmouche's moves.

In a last-minute mishap, handlers had failed to order Rousey a formidable fight-night bra and instead handed her one of the light-as-air chest coverings she usually wears for weigh-in. Now that teensy swath of fabric was the only thing standing between Rousey's goods and 13,000 onlookers at the Honda Center in Anaheim, Calif. -- and it was inching closer and closer to the mat.

"When someone's on your back trying to rip your head off, things tend to slip around a bit," Rousey says. After one failed attempt at a wardrobe adjustment, she switched her focus to freeing herself from the choke hold "so she wouldn't snap my neck in half." As soon as she flipped Carmouche to the floor, Rousey went straight for her own neckline. Bad move: "I got kicked straight in the chest right as I was trying to adjust my bra."

Rousey eventually finished Carmouche with her signature armbar. But the rumble over the bra had only just begun. Online commentators asked whether the UFC's new female fighters required a dress code to fight modestly. Others immortalized the near nip slip as an ever-refreshing animated GIF.

The episode was the latest skirmish in a long-standing war over the place of the mammary in the pectoral-dominated world of sports. Breasts are an impressive network of milk glands, ducts and sacs, all suspended from the clavicle in twin masses held together by fibrous connective tissue. But a mounting body of evidence suggests that they pose a serious challenge in nearly all corners of competition. Gymnasts push themselves to the brink of starvation to avoid developing them. All sorts of pro athletes have ponied up thousands of dollars to surgically reduce them. For the modern athlete, the question isn't whether breasts get in the way -- it's a question of how to compete around them.

"Gina Carano was an amazing fighter, and she had a fantastic rack," Rousey says of the MMA fighter-turned-actor. But then again: "You don't see big titties in the Olympics, and I think that's for a reason."

BREASTS HAVE TAKEN a metaphorical beating from the sports world ever since women first entered the arena. Greek folktales spun the myth that a race of all-female Amazons lopped off the right breast in order to hurl spears and shoot arrows more efficiently. (In Greek, a-mazos means "without breast.") Centuries later, in 1995, CBS golf analyst Ben Wright controversially told a newspaper that "women are handicapped by having boobs. It's not easy for them to keep their left arm straight. Their boobs get in the way."

Wright's commentary wasn't exactly the result of careful scientific review. ("Let's face facts here," he opined in the same interview: "Lesbians in the sport hurt women's golf.") But what if he had a point? Research shows a typical A-cup boob weighs in at 0.43 of a pound. Every additional cup size adds another 0.44 of a pound. That means a hurdler with a double-D chest carries more than 4 pounds of additional weight with her on every leap. And when they get moving, the nipples on a C- or D-cup breast can accelerate up to 45 mph in one second -- faster than a Ferrari. In an hour of moderate jogging, a pair of breasts will bounce several thousand times.

None of this feels good. Large breasts are associated with back and neck pain, skin rashes, carpal tunnel syndrome, degenerative spine disorders, painful bra strap indentations and even anxiety and low self-esteem. In one study of women racing in the 2012 London Marathon -- cup sizes AA to HH -- about a third reported breast pain from exercise. Eight percent of those described the pain as "distressing, horrible or excruciating." Reports of pain grew with every cup size.

It's no wonder that athletes rack up strategies -- and bills -- for battling the bulge. Well-endowed golfers flock to former player-turned-coach Kellie Stenzel, who teaches them to shift their posture forward so their swing clears the top of their breasts; the bigger the chest, the deeper the lean. "These women have a real feeling of relief, like, 'Nobody ever told me that before,'" Stenzel says, adding that despite Wright's claims, she's never seen a chest she couldn't coach into compliance.

American archer Kristin Braun says her chest causes clearance issues as she draws her bow; in order to get around it, she anchors the string farther away from her body, which can diminish power and consistency. Australian hurdler Jana Rawlinson received breast implants in 2008, then promptly removed them in hopes of speeding up her times. "Every time I raced, I panicked about whether I was letting my country down, all for my own vanity," she told reporters. And inside the Octagon, Rousey's boob issues go deeper than the cotton-Lycra blend. "The bigger my chest is, the more it gets in the way," says Rousey. When she's fighting at her most curvaceous weight, "it just creates space. It makes me much more efficient if I don't have so much in the way between me and my opponent."