Whether women are said to be flat-chested or big-busted, ordinary bras fall short when it comes to supporting bouncing breasts, a new study claims.
And during exercise, women's breasts bounce more than previously estimated, moving a vertical distance of up to around eight inches (21 centimeters) compared with a past maximum measurement of six inches (16 centimeters).
The bouncing, in some cases with breasts weighing 20 pounds or more, can prove painful and damaging to the limited natural support system.
While brassieres have evolved throughout history from body-binding corsets to cleavage-enhancing "miracle" bras, only recently have researchers injected a dose of science into the design of undergarments that go beyond conferring a more "perky" look, the researcher says.
"It is only recently that bra design has turned to science," said study author Joanna Scurr, a biomechanics professor at the University of Portsmouth in England. "There was no research. It’s like designing a car or kitchen equipment without first thinking 'what is the purpose of this?'"
Scurr will present her research this week at an annual meeting for the British Association of Sport and Exercise Sciences in Bath.
Scurr recruited 70 women, including students and faculty from the University of Portsmouth, with bra sizes ranging from A-cup to extra-large (DD, E, FF, G, H, HH, J and JJ were included).
Each woman walked, jogged and ran while wearing different bra types. During the exercise, Scurr took biomechanical measurements, including the amount of breast movement in three directions: up-and-down, side-to-side and in-and-out.
During walking exercise, the women's breasts moved relatively the same amount in all directions. But when participants sped up to a jog or run, their breasts moved proportionally more in some directions than others: More than 50 percent of the total movement was in the up-down direction, 22 percent side-to-side and 27 percent in-and-out.
The overall pattern of the movement resembled a figure-8.
Typically, bras are designed to minimize up-and-down motion and not the other two dimensions of breast movement found in Scurr's study.
For all cup sizes, the so-called encapsulation bras in which each cup is separately molded provided the most support, beating out the compression bras, which limit only the up-and-down motion. The encapsulation bras limit some of the movement in the other directions as well.
In A-cup women, wearing a sports bra reduced overall breast movement by 53 percent, compared with a 55-percent reduction for G-cup women.
A pair of D-cup breasts weighs about 15 to 23 pounds (7 to 10 kilograms).
But breasts have little natural support, Scurr says, although ligaments and the skin are thought to do most or all of the work. Breasts are made up of fat, milk ducts and connective tissues, such as collagen, ligaments and blood vessels. The momentum created by intense bouncing can stretch the breast's connective tissues, causing sagging and pain for many women.
An estimated 50 percent of women experience breast pain during exercise, Scurr claims.
Without appropriate bra support, some women abandon active sports due to breast pain, Scurr said.
"There really are women who want to do exercise but who don’t have the bras to cope," Scurr said. "I know of a 16-year-old who was selected to play basketball for the county, but she was told to give it up because she couldn’t find a bra that made playing possible."
Scurr is working with major bra manufacturers in Britain and globally to design a bra that minimizes breast movement in all three dimensions. The next bra, she hopes, will incorporate "smart materials" that can change to provide custom-made support for each woman and her activity level.
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Jeanna served as editor-in-chief of Live Science. Previously, she was an assistant editor at Scholastic's Science World magazine. Jeanna has an English degree from Salisbury University, a master's degree in biogeochemistry and environmental sciences from the University of Maryland, and a graduate science journalism degree from New York University. She has worked as a biologist in Florida, where she monitored wetlands and did field surveys for endangered species. She also received an ocean sciences journalism fellowship from Woods Hole Oceanographic Institution.