When women run, jump or even walk, their breasts are always in motion. And that has consequences: seven in ten women who exercise experience breast pain linked to sport. Yet for decades, the sports bra remained a blind spot in sports science. Slowly but surely, more researchers are analysing how improved sports bras can boost comfort, prevent injuries and enhance performance.
The breast as a biomechanical challenge
‘Breasts aren’t muscles,’ explains Ine Mylle, researcher in female athlete biomechanics at Simon Fraser University in Canada. ‘They consist mainly of fat and connective tissue and move independently of the torso. When you run or jump, your body accelerates and decelerates, but your breasts keep moving for a moment. That creates a three-dimensional displacement, which we call the “breast bounce”.’
During that movement, the Cooper’s ligaments — the breast’s natural support structures — are stretched. ‘If that happens too often or too forcefully, they lose strength,’ says Mylle. ‘The result? Pain, postural issues, and even long-term tissue damage. A whopping seven in ten women who exercise say they experience breast pain linked to sport.’
Less pain, more efficiency
Recent research by Veerle Segers (Ghent University) showed that for some women, breast displacement can reach 30 centimetres relative to the rib cage: 15 cm upwards and 15 cm downwards. ‘That creates an acceleration several times greater than gravity, making the breasts feel much heavier.’
‘The larger the breast, the greater the impact on the body. Stronger support makes a striking difference: a good sports bra can reduce breast movement by 60 per cent. That helps women avoid pain and move more efficiently.’
Thermal cameras and economics
So how do you design — or choose — the ideal sports bra? ‘In essence, you want to keep the moving mass – in this case the breasts – as close to the body as possible to minimise impact forces. And you want to do that without creating discomfort,’ says Gunther Steenackers, professor of Electromechanics at the Faculty of Applied Engineering at UAntwerp and the Industrial Vision Lab.
His research group develops camera-based techniques for textile inspection. ‘For example, we use thermal cameras to assess the comfort of sportswear. They capture factors such as heat dissipation, potential friction from seams, or blood flow in compressed muscle tissue.’
With thermal cameras, we capture factors such as heat dissipation, friction from seams, or blood flow in compressed muscle tissue.
The techniques exist, but they haven’t yet been applied to sports bra design in the lab. ‘The sportswear companies we collaborate with are currently focusing on areas that are more lucrative for them. For example, they look at how tiny design details can improve heat dissipation in clothing for elite male athletes. Thermoregulation can boost performance by up to 20 per cent. I’d say that’s also something worth considering when designing the ideal sports bra.’
Devised by fashion designers
Sports science for women is still far less developed than sports science for men. Most sports shoes, for instance, are designed for men and then released in ‘women’s colours’. Only this year did Adidas launch its first women’s football boot designed entirely for the female body.
Attention for female health and sport is increasing, especially in football and cycling — and soon in volleyball too, thanks to UAntwerp's Springstof project. But the lack of knowledge about sports bras highlights how little we know about injury prevention, training load or sportswear for female athletes.
Springstof: science on the volleyball court
In the Springstof project, four master students in product development at the University of Antwerp are working together with the West Flanders volleyball team VLAMVO Vlamertinge to develop the perfect sportsbra for jumping sports.
Over the coming months, the students will collect extensive data, take measurements of the players (possibly even using a 4D scanner) and develop designs and prototypes. In doing so, they bring biomechanics and practice closer together and show how science is set in motion – quite literally.
‘Most sports bras are still designed by fashion designers who lack biomechanical insight,’ says Mylle. ‘And when testing does happen, it’s often on a treadmill, but treadmill running is unnaturally straight, without any twisting or jumping.’
The right size
Another issue, according to Mylle, is that up to 80 per cent of women wear the wrong bra size. ‘Often because they choose whatever feels comfortable in the fitting room, but what feels fine while standing still may not work during intense movement. If a bra is too loose, everything moves too much; if it’s too tight, it can restrict breathing or circulation.’
Raising awareness about choosing the right sports bra may be just as important in the short term as research into new designs, Segers adds. ‘In Australia, there’s already more awareness about breast movement and comfort during sport. But even there, nearly half of elite athletes were found to be wearing the wrong bra.’
In Australia, there’s already more awareness. But even there, nearly half of elite athletes were found to be wearing the wrong bra.
The right model
Broadly speaking, there are three types of sports bras: compression bras (which hold the breasts against the chest), encapsulation bras (where each breast is supported in a moulded cup), and hybrid models. Then there are variations: racerback or regular straps, front or back closures, and so on.
What works best for you depends on your body and your sport. Segers: ‘Someone with an A cup can usually run comfortably with a simple compression top, but from a C or D cup onwards, you’ll likely need an encapsulated bra with a racerback. From an E or F cup, you often need both compression and adjustability, because breast size can also vary by up to one cup during the menstrual cycle. So you need some flexibility.’
But there’s no single perfect sports bra: it’s about what suits your body and your context. ‘Two women with the same cup size can have completely different breasts,’ Segers says. ‘That’s why we sometimes work with 3D scans to fine-tune fit and pressure distribution. And if you’re looking for guidance, check the sports bra tool at bra.edu.au.’
Measuring means understanding – also for breasts
To learn even more about the ideal sports bra, Mylle developed a new way of measuring movement. ‘For my research, I work with wearable sensors that measure breast acceleration in real-life conditions. We use the same technology as the accelerometers in smartwatches that count steps. The sensors are coin-sized and weigh less than five grams.’
The sensors allow researchers to map breast movement in three dimensions and calculate how much force acts on the breast. ‘We link that to athletes’ own experiences in real sports settings – pain, pressure, discomfort,’ says Mylle. ‘That way we don’t just know what’s moving, but also how it feels.’
My research aims to help women move more freely and to narrow the knowledge gap with male sports health.
Ready for the ideal bra?
Are there other techniques or materials that can help us design the sports bra of the future? Steenackers: ‘A major trend is digital prototyping, or digital twins. Instead of testing dozens of trial subjects, we increasingly build digital models of bodies and clothing designs. This allows us to perform virtual experiments and optimise designs with minimal physical testing.’
‘I also believe in the potential of personalisation and smart materials. With body scans, we can use someone’s exact body shapes to create a seamless custom bra that prevents skin irritation. And smart fabrics are materials that adjust their elasticity or heat dissipation depending on the activity. These materials already exist, but they’re still expensive. For now, you’re probably better off using different bras for different sports.’
From bras to the health gap
It’s still hard to predict how the ideal sports bra will evolve. ‘But it’s clear there’s still a lot of progress to be made,’ says Mylle ‘For one thing, I don’t believe in one universal model. Just as you choose running shoes based on how intensely you run, you should choose a sports bra based on your breast movement and training load.’
‘For me, good bra design isn’t just about helping women perform better. It’s also about equality and wellbeing. My research aims to help women move more freely and to narrow the knowledge gap with male sports health.’
Health gap in the spotlight
The health gap remains a real problem, not only in sports but also in other areas. Professor of cardiology Emeline Van Craenenbroeck explains that a heart attack in women, for example, looks very different from a heart attack in men – and recognizing these female-specific symptoms is a matter of life and death.