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The Best Sports Bras, According To Rigorous, Sweaty Testing

The best sports bra has to pass a lot of tests: It needs to be supportive but not painful; compressive but not so tight that you pop out the top; breathable but thick enough that it provides nipple protection; and it should be comfortable, of course.

The best sports bras provide the right mix of support, comfort and breathability.

ILLUSTRATION: FORBES / PHOTO: RETAILERS

I spent 3 months testing sports bras so you don't have to. I looked at more than 40 bras and tested 10 while running, practicing yoga and Pilates, carting my young children around and simply living my life. Then I enlisted a panel of women of various sizes to test out the best seven options. In the end, we decided that the Nike Swoosh Non-Padded Sports Bra, an OG in the sports bra space, was the best overall sports bra we tried. But sports bras are a very subjective purchase, so we also picked options for high-impact activities, yoga and athletes with larger busts.

The following is a list of all the winners from our extensive testing process:

How I Tested The Best Sports Bras

For this guide, I spent several hours researching the best sports bras. I read online reviews, digested many different sports bra guides and read about bra fit and style. Sports bras come in many different constructions—compression bras and encapsulation bras being the most common, in addition to hybrid bras that combine both features—and I learned that different bra styles will work better for different body types. The best sports bra for you will also vary based on the kinds of movement you prefer.

We also consulted with several experts: Joanna Wakefield-Scurr, a professor of biomechanics at the University of Portsmouth, taught us about what features to look for in a good bra. Dr. LaJean Lawson, an apparel expert who serves as an advisory board member for the Outdoor Product Design and Development program at Utah State University, spoke to us about how to find bras for larger-breasted women. Finally, Kim Mock, a plus-size athlete, photographer and adventurer, gave us real-life feedback on the types of bras she prefers for her active lifestyle.

These conversations helped me narrow down our test list to 10 sports bras with solid reviews. Each had the features most people will need to keep their breasts from moving around during exercise. I ordered these bras using the fit guides on each brand's website, and then tested them in three different environments:

First, I simply tried them on and took notes about adjustability and fit.

Then, I wore each bra to a low-intensity yoga class.

Finally, I wore each bra for a high-intensity, sweaty workout (a HIIT class or a run).

I also washed each bra at least three times, according to the brand's instructions, to test for durability.

Each woman on the panel tested the bras in the same way I did; they wore them for low-intensity and ... [+] high-intensity workouts, washed them and submitted feedback.

Jenni Gritters For Forbes

Once this round of testing was complete, I recruited six women from the Forbes Vetted team to try out the bras. They ranged in size from 32A to 42DDD. Each woman on the panel tested the bras again in the same way I did; they wore them for low-intensity and high-intensity workouts, washed them and submitted feedback. I compiled all this data into a spreadsheet that showed me the best sports bra options for people who want to pursue different activities with their unique bodies and needs.

Nike.Com

Nike Swoosh Non-Padded Sports Bra

Style: CompressionSupport: MediumSize range: XS to 2XLMaterials: Polyester and spandex

Best for:

High-movement activities like yoga or Pilates

A to C cup sizes

Sweaty workouts

Skip if:

You need more support for running

Your cup size is D or larger

The Nike Swoosh Non-Padded Sports Bra is a simple compression-style bra that's been around for ages. In fact, this is probably the bra you imagine when you think of a classic sports bra—and for good reason. The fabric is thick, with a polyester-spandex blend that has enough give to not be uncomfortable but that still holds your breasts in place. The nylon-spandex hem is soft against the skin, preventing chafing. (And at least 50% of the fibers are recycled, according to Nike.) These materials also wick sweat well; after a sweaty workout, I found that the bra was dry within about 30 minutes.

At just $35, this bra is a workhorse. You can wear it hard and machine-wash it without worrying too much about needing to replace it. We found that there was no wear and tear after our first month of heavy use. I preferred the Swoosh for yoga and Pilates classes; it stayed in place during lots of twisting and moving. It wasn't, however, quite supportive enough for long runs.

"I really appreciated how simple yet effective the Nike was," said one of our testers. "At first, it seems just like a band of fabric across your chest; the design is so simple. But then I realized there's a lot of genius in what looks simple. The exact proportions of this bra are amazing: the length of the straps, the perfect snugness of the fit, the comfort of the band. I took the Nike Swoosh for granted (how hard can it be to make a good sports bra?), but now I understand why everyone is obsessed with this bra!"

Here's the kicker, though: The Nike Swoosh is a compression-style bra, which means that it flattens your chest versus encapsulating each breast. This style of bra really only works well for people with smaller cup sizes, usually A through C, and sizing is a bit tricky because you can only order it based on a small, medium or large sizing chart, rather than adjusting to your rib cage and cup size. (Most of our testers were happy with the sizes they ordered, but the ones who liked it most were in the A and B cup size range.)

Although Nike does offer the Swoosh in a 2XL size, which they say will fit anyone with a 40D to 42C cup size, we think this bra is best suited for people with smaller breasts who like a compression-style fit. You can also order the Nike Swoosh in a padded version. With only a few exceptions, all Nike products have a 60-day return window; the items must be unworn.

Style: Hybrid encapsulation and compressionSupport: Low to mediumSize range: S to 3XLMaterials: Nylon, polyester and spandex

Best for:

High-movement activities like yoga or Pilates

Some running

Athletes who churn through bras quickly

Skip if:

You need more support

You want something that lasts

Fittin Racer Back Sport Bras come in a four-pack for under $40, rendering them the cheapest sports bras we tested. More than 57,000 reviewers have given them an average of 4.4 stars on Amazon, which intrigued me during my research process—and after testing them, I can see why. The Fittin bras aren't the best of the bunch, but they're certainly a solid choice for the price. As one tester summed it up, "They seem like a good version of your typical, low-cost sports bra."

The Fittin bra has a hybrid construction, with a compression-style material and fit and padded encapsulation stitched around each breast. The nylon-polyester-spandex blend certainly feels cheaper—and it pilled a bit more after a wash—than that of the other bras in this list, but the Fittin still wicks moisture well during hot workouts.

The Fittin bra stayed in place during pretty much any kind of workout I tried, and offered enough support for my B-cup breasts on shorter runs. One of our larger-breasted testers said that this was a great lounge bra because it was comfortable and soft, and it also worked well for hiking. But several others cautioned their fellow large-boobed compatriots against running in the Fittin—they didn't find it to be supportive enough.

This bra was the most loved by our testers who had medium breast sizes, usually in the C to D range. The Fittin bra runs small, so most of us ordered a size up; those who didn't, experienced chafing under their arms. Also, as with most cheaper bras, the pads come out of the Fittin bra when you dry them, and you'll start to notice some material fuzziness over time. This is more annoying than anything else, as you can just stick the pads back in, but it can be a chore to hunt the pads down each time you want to wear the bra.

Fittin bras are from Amazon, so you're beholden to Amazon's fairly decent return policies.

SHEFIT

SheFit Ultimate Sports Bra

Style: Hybrid compression and encapsulationSupport: HighSize range: XS to 6LuxeMaterials: Nylon, polyester and spandex

Best for:

HIIT classes, running

Any cup or band size, but especially larger sizes

Jumping or cardio

Style and aesthetics

Skip if:

You don't need lots of adjustable straps

You want a bra that's great for flexibility practices

The SheFit Ultimate Sports Bra is a much-loved and much-hated sports bra, depending on your body type and activity needs. Still, the testers who loved the SheFit loved it more than any other bra they tested. The SheFit Ultimate Sports Bra is an encapsulation-style bra with compression. It has adjustable shoulder straps, incredibly thick nylon-blend fabric and a zipper down the front. Compared with most of the sports bras we tested, this one is definitively more stylish. It also comes in a wide range of sizes, from XS to 6Luxe (which fits cup sizes up to I).

The testers who loved it all had D or larger cup sizes, and they were excited about how it kept them held in without feeling suffocating. This is due to the stretch panels along the sides and seamed cups, which feel less restrictive than you'd expect.

But those who didn't love it felt like the SheFit was too supportive. They hated the rigid, stiff fabric and the many points of adjustment. "You can really tell you're wearing this," one tester said. "It almost feels diaper-like, in that it's bulky and thick and shows beneath your clothes."

All of our testers agreed that the SheFit required a lot of adjustments. You'll have to adjust the back of the bra first, then the hook-and-eye shoulder straps. I had to adjust this bra about six times to get the right fit, although once the fit is correct you likely won't need to fix it again.

"The SheFit is a cute option," one larger-breasted tester said, "and it's good for certain things. I liked it for middle-distance running, but it was less good for anything where I had to bend over because I popped out the top."

Everyone also agreed that sizing up was the right move for the SheFit, usually just by one cup size. It's a rigid option but offers support at any size. SheFit bras are part of the brand's "Game Changer Promise" program; this means you can return them within 30 days, no questions asked, even if you've already worn them. You will have to pay a small fee for return shipping.

Nordstrom

Wacoal Simone Sport Underwire Bra

Style: EncapsulationSupport: HighSize range: 32C to 42IMaterials: Nylon and spandex

Best for:

Larger breasts

Those who want a sports bra with underwire

Work-to-workout transitions

High-intensity workouts

Skip if:

You have smaller breasts

You prefer compression to encapsulation

Wacoal has been making women's bras since 1946, and the Simone Sport Underwire Bra has long been a favorite for women with larger breasts. Our testers gave this bra mixed reviews; most of them loved its functionality, but a few didn't love the "grandma" style of this underwire bra. A few complained about how the bra looked under a shirt.

That said, the Simone was definitely meant for larger-breasted people. Most of our largest-breasted testers obsessed over how comfortable the Simone bra was, even if it wasn't the cutest option in the lineup. It hit that nice balance between supportive and comfortable, and it kept everything in place even during high-intensity workouts. This isn't a bra for everyone, but if you struggle to find enough support for your breasts during jumping or running workouts, this one is worth considering.

In addition to its own site and Amazon, Wacoal bras are sold online through Nordstrom, where you can return it at any time.

Style: CompressionSupport: LowSize range: XXS to 6XLMaterials: Recycled plastic bottles and spandex

Best for:

Lounging

Yoga

Pilates

Everyday wear

Skip if:

You need more support

You plan to run

Our middle-sized testers, in the B and C ranges, loved the Girlfriend Collective Paloma Racerback Bra. It was my favorite bra—so great, in fact, that I quickly ordered two more to add into my exercise rotation. The Paloma is made with spandex and the brand's classic recycled plastic bottle material. (Paloma's reputation for sustainability is nearly unparalleled in the yoga gear space.) The material is so soft that I didn't want to take the bra off, and it wicked moisture well even during hot yoga classes, at temperatures above 100 degrees.

Our smaller-breasted testers found the Paloma to be a bit boxy; this caused gapping in the sides. Our larger-breasted testers thought this compression-only option didn't provide enough coverage. But if you're in the middle of the size chart, like me, you'll likely find the Paloma to be both supportive enough for a workout class (but probably not for a longer run) and comfortable enough to wear around the house. It hits mid-ribs, so the cut is also flattering for most body types.

"It's so comfy it feels like I'm not even wearing anything," one tester said. "I wear this often as a regular bra even when I'm not working out."

Girlfriend Collective offers 30-day returns. When you're finished with any Girlfriend Collective product, you can recycle it through the brand's ReGirlfriend program.

Other Products Tested

We tested five other products that didn't make the cut.

Lululemon Energy Bra High Support: This bra was tight, with too many straps and too much compression. While I've worn (and loved) Lululemon apparel for many years, this compression-style bra just wasn't a favorite. It was hard to get the straps to lay flat and the fabric is restrictive. There's a hook feature that allows you to extend the bra around your rib cage, but the buckles on the band often get stuck, making it hard to put this bra on and take it off.

On Performance Bra: If you have an A or B cup size, you might find the On Performance Bra to be an appealing option. My editor, who wears a size A, raved about the seamless, compression-style construction (with slight padding built into each cup) and regularly wears the On Performance Bra for her weekly 4-mile runs. "It's supportive, comfortable and feels invisible when I'm wearing it," she says. But I found the compression to be too intense for my size B cup, plus the straps chafed, which just proves how your sports bra choice really is very personal to your body type. (I also tried the Active Bra from On and found it to be equally gappy in the cups but tight under the arms and around my rib cage.)

Brooks Dare Crossback Run Bra 2.0: Butter-soft and seamless, I wanted to love this compression-style bra (with a slight nod to encapsulation via minimalist stitching). And I did find myself reaching for it on occasion after I finished up my testing, mostly for runs around the block. But the bra wasn't a good option for exercise classes, as it gapped under the armpits and across the chest. If you try to bend or twist during a yoga class, you risk exposure. The fabric also felt a bit thin for a longer run, and every single tester messaged me to ask if they'd gotten the wrong size because of the prominent gapping.

Panache Non-Wired Sports Bra: This compression-style bra offered a nod to encapsulation, with formed cups, but it fit tight and small. It was very hard to make adjustments to the thinner straps—the buckles kept getting stuck—and the seams pressed uncomfortably against my skin. Even though this was supposed to be a great option for people with larger cup sizes, even our smaller-breasted testers found it to be just subpar.

Champion Spot Comfort Full Support Bra: Don't discount this budget, encapsulation-compression hybrid bra. It didn't make our favorites list, but a few larger-breasted testers gave it high marks because it "simply did its job." The Spot has more points of adjustment than almost any other bra I tried, but the straps are more effective than those on the Lululemon bra. However, because of all these points of adjustment, there's also more potential for chafing. The cut of the bra is also interesting, with a neckline that some people preferred and some found annoying under a shirt. It's not the most flattering, but if you have larger breasts and you're looking for what one tester called "the utility choice," the Spot is worth a look. Fair warning: Everyone who tested this recommended sizing up by at least two sizes on the band, which is tight. Band sizing also only goes up to a 42.

How To Pick A Sports Bra

In short, a sports bra is a garment you wear to keep your breasts from moving during active pursuits. Bouncing breasts can hurt your back via tension on the Cooper's ligaments. Sports bras were created to combat this bouncing by offering support through a band around your rib cage, shoulder straps and either compression across your breasts, encapsulation of your breasts or a combination of both.

Style: Compression Vs. Encapsulation

Compression bras flatten your breasts with tight material. They usually can't be adjusted, and they tend to come in smaller sizes, usually just in small to large variations versus a cup and band size. Compression bras are known to cause "uniboob," where your breasts are smashed together into a blob-like shape. This is especially problematic for women who have larger breasts, as it can be uncomfortable and damaging over time. But women with smaller breasts may prefer compression bras for comfort and simplicity.

Compression bras usually can't be adjusted, and they tend to come in smaller sizes, like the Nike ... [+] Swoosh.

Jenni Gritters

Encapsulation bras separate your breasts into two cups. Most encapsulation bras have cups, although some have seaming, underwire or molding to divide out the two compartments. Encapsulation bras come in those familiar sizing metrics (a cup size and band size), which means it can be easier to find a more supportive fit for your unique body. You'll also want to try an encapsulation bra on at a store, though, or opt for a bra that you can return for free; sometimes it takes a few tries to get the sizing right.

Encapsulation bras, like the Wacoal Simone Sport Underwire Bra, come in a cup size and band size, ... [+] which means it can be easier to find a more supportive fit for your unique body

Jeni Gritters

"A lot of people and a lot of sports have a preference more toward crop top designs that compress and flatten the breasts," Joanna Wakefield-Scurr, a professor of biomechanics at the University of Portsmouth, told us. "But that is not often the best way to support the breasts.

I would definitely suggest looking at more encapsulation designs. The challenge is that they are harder to fit because there's less stretch in them; an encapsulation bra will not adapt as much to shape and size. You may have to shop around a bit more to find an encapsulation bra that works for you."

"If the bra is just generic sizes of S to 4X, it's probably not going to fit too well," athlete Kim Mock agreed. "Buying a sports bra should be more like buying a regular bra."

Combination bras are becoming more and more popular; they combine compression and encapsulation to give you both support and structure. Runners will find this style to be the most comfortable because compression assists with up-and-down movement, while encapsulation keeps your breasts from moving side to side.

Shoulder Straps And Bands

No bra can totally stop breast movement, especially if you're attending a HIIT class or running. But your breasts should at least stay in the bra—no spilling out the top or gapping along the sides.

The band at the bottom of the bra needs to be comfortable, and it's the key to preventing slippage. Ideally, the band should be on the wider side, which allows it to lie flat. Some bands are adjustable, which is helpful because you can make sure they don't dig into your rib cage or move around. Riding up or down is a no-no.

"For larger-breasted women, you'll want to make sure to find a sports bra that has a firmly fitted underband that doesn't ride up in the back," says Wakefield-Scurr.

Adjustable straps tend to be useful for getting a good bra fit that's both comfortable and supportive, too. While I loved some of the adjustment situations more than others in our testing pool, I did generally appreciate a Velcro or slider-style strap that helped me get a snug fit. Most of the bras I tested had racerback straps or U-back straps.

"The strap can really put strain on the shoulder and cause irritation," says Dr. LaJean Lawson, sports bra innovator and expert. "The larger the breasts, look for a cushier strap. If the shoulder strap is double the width, it can cut the pressure on the shoulder almost in half."

Material

A good sports bra should have some spandex in it, so it's not completely rigid. But if it's all spandex, there won't be enough support for your breasts while you move, either. That's where the other fabric—usually nylon or polyester—comes in. Ideally, a sports bra should also wick moisture so your sweat moves away from your body as you exercise. The quicker the material dries, the better. Cotton is generally a no-go for active apparel because it doesn't dry quickly; merino wool sports bras are becoming increasingly popular for long-distance outdoor adventures.

Return Policy

Because it can be tough to get the right fit on the first go, especially when you're ordering online, look for brands that allow you to easily send a product back, or trade it in for a new size.

How Should A Sports Bra Fit?

Typically, you'll want to buy a sports bra in the same size as your regular bras. Sports bras might be more compressive than your everyday bra, but that doesn't change their sizing. If you've never measured yourself before, I love this Reddit guide to bra sizing. Check it out and measure your breasts before ordering a sports bra.

Ideally, a sports bra should fit securely. The straps should lie flat on your shoulders, and the band should be tight but not painful; it should not roll up or sag down. Gapping along the sides is a sign of poor fit.

Is It Okay To Wear A Sports Bra Every Day?

Yes! Many of the bras listed in this guide are supportive and comfortable enough to wear every day. If you don't like the compression of a sports bra, you may opt for a more lightweight option—or a bra with underwire—when you're not exercising. But there's no reason to relegate sports bras to workouts alone if you like how they feel.

How Can I Find A Good Sports Bra For Large Breasts?

"Larger-breasted women have been underserved for so long," Dr. Lawson says, noting that breast sizes have gotten larger over the past four decades or so, but the sports bra industry has been, in general, slow to respond and understand the forces present for someone with larger breasts.

"There's more diversity now in women's bodies, but manufacturers have been lazy. Bras need to be larger and stronger so we can all look good in our gear," she says. "Women are entitled to products that allow them to be active but that are also attractive."

For women with larger breasts, a bra with more volume inside the cups can be helpful. Bras also need to be more structured, as the movement of larger breasts exert more force on the body. And you'll want to make sure you have a supportive band and straps; the thicker, the better. Depending on your body type, some women with larger breasts will also prefer a bra with a higher cut, meaning that your breasts can't pop out the top when you lean over.

My Expertise

I'm a freelance journalist who's been writing product reviews, health content and more for over a decade. Before I started freelancing, I worked as a full-time editor at Wirecutter, where I reviewed and wrote about outdoor and travel products. Since then, I've worked on product-focused content for Reviewed, Slate, Wirecutter, Gear Patrol, REI and others. Most of my reviews these days are focused on health, the outdoors and baby and kid gear.

In addition to being a writer, I'm also a mom to two tiny humans—a 3-year-old and a 9-month-old—and I'm a certified yoga instructor and amateur runner. I live in a mountain town and try to exercise at least 4 days per week, usually Pilates or yoga. I also walk or run outside, often with my kids, nearly every day.

The Right Sports Bra Could Increase Your Running Performance By 7%

Running is one of the most accessible forms of exercise with an array of proven cardiovascular and musculoskeletal benefits, and an added bonus of increased mental health. Good-quality running gear, such as the right pair of shoes, is vital to improve running performance and reduce injury risk. For women particularly, a well-designed sports bra protects from exercise-induced breast pain, which can be a significant barrier to practicing sports. Up to 72% of women experience breast pain while running.

Previous research has shown that the increased breast support sports bras offer not only influences breast movement but can also positively influence running performance. Greater breast support has been linked to lower oxygen consumption and better range of motion.

Dr. Douglas Powell and Hailey Fong and colleagues at the Breast Biomechanics Research Center at the University of Memphis wanted to further investigate the effect of a good sports bra on running biomechanics, and have now published new findings in Frontiers in Sports and Active Living.

"The biomechanics underlying improved running performance with greater breast support are not well understood. Our study represents one of a series of research studies on the topic of breast support and whole body biomechanics," explained Powell. "We wanted to identify strategies to reduce activity-induced breast pain for females, a group that makes up approximately 50% of the population."

Biomechanics of running

Specifically, Powell and his colleagues looked at the influence of breast support on knee joint stiffness during treadmill running. Knee joint stiffness is a biomechanical measure that indicates how resistant the knee joint is to movement when force is applied. Knee joint stiffness has been associated with lower oxygen consumption, improved running performance, and running-related injury.

A sample size of 12 recreational runners, aged between 18 and 35 years, with a self reported B-, C-, or D-cup, was professionally fitted with two different sports bras: a high support bra and a low support bra. For the control condition, the participants were asked to perform the experiment bare chested. Each participant then performed three-minute running bouts in each of the three randomized breast support conditions (high, low, bare/control).

To collect the data the researchers used a 10-camera motion capture system and instrumented treadmill. The movements of the participants were tracked using individual retroreflective markers fitted on different parts of their bodies. The researchers used Visual3D to calculate knee joint excursions, while custom software was used to calculate knee joint stiffness and breast displacements during the stance phase of running in each experimental condition.

The importance of good support

The experiment showed that increased levels of breast support were associated with greater knee joint stiffness due to smaller joint excursions. Compared to the control condition, the low and high support conditions were associated with 2% and 5% increases in knee joint stiffness respectively. Overall, taking into account these results and results from previous research by Powell and Fong, a high support sports bra can improve a female's running performance by 7%.

"The findings show that breast support not only influences movement of the breasts but that compensations occur across the entire body," said Powell. These compensations can lead to reduced running performance, increased injury risk, and even the development of chronic pain such as back and chest pain.

Powell continued, "Over the past 50 years, limited evolution in bra design has occurred. Our findings, in conjunction with previous research studies, show that sports bras should be considered not only as apparel, but also as sports equipment that can both improve performance and reduce the risk of injury, playing a role in women's health."

More information: Increasing breast support is associated with altered knee joint stiffness and contributing knee joint biomechanics during treadmill running, Frontiers in Sports and Active Living (2023). DOI: 10.3389/fspor.2023.1113952. Www.Frontiersin.Org/articles/1 … or.2023.1113952/full

Citation: The right sports bra could increase your running performance by 7% (2023, April 21) retrieved 28 April 2023 from https://medicalxpress.Com/news/2023-04-sports-bra.Html

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A Good Sports Bra Can Boost Your Running In A Surprising Way

For many of us, bra shopping is roughly as fun as a colonoscopy. But a new study offers one good reason to stick with it: The right sports bra may help make us better runners.

Nearly 3 in 4 women experience breast pain while running, often due to a combination of larger breasts and an ill-fitting or unsupportive sports bra, researchers note in a new study published in Frontiers in Sports and Active Living.

A good sports bra can reduce breast pain, the researchers found, but its benefits go beyond that: A supportive, well-fitting bra can also change how much the knees flex during running, improving performance.

"The human body typically optimizes cyclic movement patterns for walking and running toward metabolic efficiency," says lead study author Douglas Powell, PhD, director of the Breast Biomechanics Research Center at the University of Memphis in Tennessee. "By removing or reducing the constraint of breast motion, the neuromuscular system can perform in a more metabolically efficient manner."

The new study complements research published last year in the same journal that found that supportive, well-fitting sports bras can improve running performance by 7 percent by helping runners use oxygen more efficiently.

Study Subjects Ran With Low-Support Bras, High-Support Bras, and Bare-Chested

For the new research, researchers wanted to see how reducing breast motion with a more supportive bra during running might affect a biomechanical measurement known as knee joint stiffness. While the issue remains under investigation, a body of previous research has suggested that the stiffer the knee joint, the greater a person's running efficiency.

Researchers had twelve recreational runners ranging in age from 18 to 35 years old who wore bra cups in size B, C, or D get professional bra fittings for two different sports bras: one with high support that allowed less breast movement and one with less support. Each participant then ran on a treadmill three times, once with each of the different bras and once bare-chested.

While women ran, scientists used motion capture cameras and 3D software to calculate knee joint stiffness and the amount of breast movement.

With a low-support bra, the runners had 2 percent more knee joint stiffness than they did when they ran bare-chested, the study found. And with a high-support bra, the runners had 5 percent more knee joint stiffness than when they were bare-chested.

A Good Sports Bra Matters for Many Reasons

One limitation of the study is that it's too small to be representative of all recreational runners, the study team notes. It's also unclear whether the results would apply to women who have avoided running due to breast pain but want to try again with a more supportive bra.

Even so, the results should serve as a reminder to female runners to think carefully about how their bra might impact their workout experience, says Nicola Brown, an associate professor of female health and performance at St Mary's University Twickenham in England.

"If breasts are not appropriately supported they can move independently from the body during exercise," says Brown, who wasn't involved in the new study. "This movement can alter running mechanics, muscle activity, breathing frequency, perceptions of effort, and can deter women from exercising due to pain or embarrassment."

Tips on How to Buy a Sports Bra That Fits Right

To get a good fit on a sports bra, women should look for a firm band under the breasts that sits level around the body without any gaping or puckering of the cups or breasts spilling out of the cups, Brown advises. It's easier to get a good fit when it's possible to adjust both the band and the straps, Brown adds.

"It is a good idea to try on your sports bra and have a jump around in the fitting room to check if it is supportive enough and feels comfortable," Brown says.

And even when you find the perfect fit, it's important to know the best sports bra won't keep its shape forever, Brown adds. "If you feel your breasts moving excessively during exercise, or experience any pain or discomfort during activity this suggests that your sports bra may not fit properly or may need replacing."

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