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The science behind finding the perfect sports bra

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Insufficient breast support is a barrier to exercise for many women, but with the right sports bra, there can be less bounce in your step.

Even small-breasted women can have breast discomfort while exercising. But the larger her breasts, the more likely a woman is to experience pain and tenderness during physical activity, particularly vigorous types such as jogging, aerobics, competitive tennis and even horse riding. According to Australian researcher Celeste Coltman, just 2cm of breast motion can cause discomfort during exercise. Given that larger breasts, if not properly supported, can move up and down by up to 19cm while running or jumping, it’s hardly surprising she has found that breast size affects both how much exercise women do and how vigorously they do it.

In a recent study published in the Journal of Science and Medicine in Sport, Coltman reported that those with “hypertrophic” breasts (a volume of 1200ml or more) did significantly less weekly physical activity than those with small breasts (less than 350ml), and also 53% less vigorous-intensity activity.

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The larger the breasts of the 355 women in the study, the more likely they were to agree that breast size affected their physical activity.

Coltman, now an assistant professor of sport and exercise science at the University of Canberra, did the research while completing a PhD in breast biomechanics at the University of Wollongong, home to Breast Research Australia (BRA).

She says breast size is often overlooked as a factor that discourages women from exercising. This is particularly true for the overweight or obese, who are also more likely to have large breasts. Of the 43 women in her study with hypertrophic breasts, 77.6% had a body mass index (BMI) of 30 or more (the definition of obesity), compared with just 3.1% of the 98 women with small breasts.

In previous research, Coltman found that those with an overweight BMI (25-29.9) had twice the breast volume on average of those with a non-overweight BMI, and obese women had three times the volume.

“When you consider how prevalent being overweight or obese is worldwide, if women can’t find a bra because their breasts are so large, that’s a real barrier to activity. We need to have garments designed to fit them and they need to be high-support garments.”

Celeste Coltman. Photo/Paul Jones UOW/Supplied

Other research has found that the average breast volume of Australian women is 650ml – well above the 500ml thought to require proper support during exercise.

In other words, more than half of all women need good support during exercise.

The average woman does not have access to the three-dimensional scanner that Coltman used to measure breast volume. However, cup size provides an approximate guide: women who take a D-cup or larger are likely to need a good-fitting, well-constructed sports bra during exercise. In some cases, depending on how vigorous the activity is, they may need to wear it with a tight-fitting crop top.

“Ultimately, you need to be comfortable and supported to do the activity you want to do.”

Coltman recommends getting fitted by an expert, although she notes that bra-fitters are something of a dying breed. Instead, women can use an app developed by BRA to help them find the right sports bra, although preferably by trying the garment on in a shop rather than buying it online.

Coltman says a sports bra needs a firm band: “You might need to go down a band size from your everyday bra, as it needs to be tighter and firmer.”

Because of the way bra sizing works, that may mean going up a cup size to get the right fit. The bra should be made of breathable fabric and have wide straps.

Coltman recommends running on the spot to test the bra’s level of support: ideally, total vertical breast movement should be no more than 10cm. BRA’s app includes a handy “bounce-o-meter” to help measure this in the changing room.

Coltman says finding the right sports bra can be a revelation. “A lot of women have never had a sports bra that’s supportive and fits them properly, so they don’t know what it feels like. They just keep plodding along wearing the same bra.”  


This article was first published in the June 1, 2019 issue of the New Zealand Listener.