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Your Sports Bra Could Level Up Your Running Game—With The Right Support 

Emerging research shows greater breast support correlates with increased knee joint stiffness. Find out why that is good for running efficiency.

Photo: Getty

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Every athlete with breasts knows the feeling: You’re sprinting the last 200 meters on the track, smashing a volley at the net, or jumping for a free throw. Your sports bra shifts out of place and your breasts/boobs uncomfortably bounce to-and-fro. This isn’t just annoying; it’s painful and it can ruin a workout or sideline you.

This dreaded experience is all too common: Up to 72 percent of women report breast pain when physically active. During one hour of slow running, breasts bounce an estimated 10,000 times—and the higher breasts bounce, the more pain results. A well-designed and supportive bra can reduce this breast displacement by sixty percent compared to wearing no bra. Yet relative to the millions of dollars invested in research and development to build the perfect running shoe, sports bras are often overlooked as performance tools.

Emerging research published in the journal Frontiers in Sports and Active Living shows that increased breast support can have performance-enhancing and injury-reducing effects—making sports bras protective equipment, not just undergarments. The right sports bra can improve running form, boost running performance by an estimated seven percent, and cut down on some of the common features associated with ACL injury.

“We should begin to consider sports bras to be important components of athletic equipment rather than just apparel,” Doug Powell, study co-author and director of the University of Memphis Breast Biomechanics Research Center, tells Women’s Running. “Sports bras protect the human body from insult or injury,” Powell adds, comparing sports bras to shin guards for soccer or helmets for American football and lacrosse.

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Sports Bra Science

Despite the fact that half of the population will develop breasts, the science behind breast structure and motion is limited. To help fill this research gap, Powell and his colleagues rounded up 13 recreational runners and had them hit the treadmill for three, three-minute running bouts at whatever pace they found comfortable. Participants ran without a bra, with a low-support bra, and in a high-support option. Researchers used a 10-camera motion capture system, Visual 3D, and custom software to track the runners’ knee extensions, knee joint stiffness, and breast movements during the sessions.

In this study, scientists zeroed in on knee joint stiffness, which indicates how resistant the knee joint is to movement when force is applied. This factor is associated with better running performance and speed as well as reduced running-related injury. It’s also linked with lower oxygen consumption—a key performance metric, especially for endurance athletes and distance runners, that signals physiological efficiency.

With greater breast support, study participants had greater knee joint stiffness (two percent higher in the low support condition and five percent higher in the high support condition compared to the no-bra condition) as well as increased knee extension power.

The sample was relatively small, and only included women 18-35 with self-reported B,C, and D-cup sizes. It’s too early to apply the findings to the broader population of female athletes, although Powell expects to see similar results in future experiments.

These latest findings jibe with a 2022 study out of the same biomechanics lab, which were also published in Frontiers in Sports and Active Living. Powell’s team looked at low-support and high-support bras on 15 female runners who performed 10-minute treadmill sessions. They found that increased breast support led to a seven percent reduction in oxygen consumption and improved running economy. The 2023 study showed that knee joint mechanics may be partially responsible for that seven percent performance boost.

Taken together, the team’s research shows that sports bra support not only alters the movement of the breasts and the comfort of exercise for women, but changes how they move during that exercise, Powell explains. To reduce the painful side effects of running without a sports bra or with a flimsy, low-support option, women’s bodies subconsciously compensate. Women “brace” for their breast motion by keeping their upper arms closer to their sides, while pelvis and torso rotations are limited. When breasts are well-supported, women’s arms, pelvis, and torso move more freely and effectively—freedom which translates to faster finish times and points on the board.

RELATED: Thanks to Enterprising Runners, Sports Bras Don’t Suck As Much As They Used To

The Search for a Great Sports Bra

Since the original “jogbra” hit the market in 1977, sports bra design has evolved from Nike’s first compression bra in 1999 to a sea of options for athletes like Lululemon’s “bras you can believe in” to Outdoor Voices bras designed for #doingthings.

Sportswear companies are increasingly focused on helping women feel better when active. Still, despite an abundance of choices, women often endure a frustrating trial-and-error hunt to find a sports bra that doesn’t pinch, dig in, slide, or stretch. Put simply, people want a bra that holds breasts in place, but doesn’t feel like a straight-jacket.

​​The new data doesn’t outline a playbook for choosing the right sports bra to achieve peak performance. But it does show that greater support can give athletes a crucial edge, so sportswear companies should incorporate the latest science on women’s bodies into their design.

For now, female athletes may have to conduct their own experiments by ordering a few supportive sports bras then putting them to the test. This handy sports bra calculator from Breast Research Australia can also help people find the perfect fit based on cup size, age, and activity level.

“Much like shoes, we can enjoy the designs and colors and patterns, but we really need to focus on the function of the sports bra and selecting the right sports bra for the purpose of controlling breast motion,” Powell says.

RELATED: Why It’s Finally Time to Upgrade Your Sports Bra

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