Sports Bra Sizing: How Should a Sports Bra Fit

Team WIT is proud to partner with our resident Doctor and female health advocate Dr Hazel Wallace BSc (Hons), MSc, MBBCh, also know to many as The Food Medic (@thefoodmedic), to help highlight the importance of breast health and choosing the correct Sports Bra for your body and your activity type. 



Did you know the very first sports bra was made out of two jock straps sewn together? Fed up with breast pain whilst running, and the discomfort that her regular bra caused, Lisa Lindahl created the first sports bra in 1977 called the Jockbra - and paved the way for women in sport and exercise.

Despite the progress we have made with sports bra development, not all sports bras are scientifically informed to provide adequate support for intended purpose  and, to add to that, most women don’t know what they’re looking for in a sports bra or how to correctly fit it - but this is where we are here to help. 


Why is it important?

The wrong sports bra, or the right sports bra that is poorly fit, can lead to breast pain, breast ptosis (a.k.a sag), embarrassment, negatively affect performance and act as a barrier to exercise. 

Breast pain

The prevalence of exercise-induced breast pain has been reported in a whopping 72% of exercising females (1). Over a third of female runners surveyed at the 2012 London marathon reported breast pain - with 17% reported it affected their participation (2).

While the source of exercise-induced breast pain is surprisingly not yet clear, studies have linked it to the displacement of the breasts - and not just up and down, but also side to side, and forwards and backwards. From the research, unsupported breasts move 1cm vertically in walking, up to 15cm during running, and almost 19cm during a jumping jack (3-5). If left unsupported, this repetitive motion can strain and stretch the Coopers ligaments - the fibrous, relatively weak connective tissue that help to  hold the breast up. The amount of movement and breast pain increases with the type of exercise (i.e. low vs high intensity exercise) and also the size of the breast. 

The wrong sports bra, or the right sports bra that is poorly fit, can lead to breast pain, breast ptosis (a.k.a sag), embarrassment, negatively affect performance and act as a barrier to exercise. 

Barrier to exercise 

Poor breast support can ultimately prevent women and girls from taking part in exercise and sport - which has a huge knock on effect on overall health. One study found that 17% of women consider their breasts as a barrier to exercise, closely behind energy and motivation (#1 reported barrier), time constraints (# 2), and health (#3) (6). The same study also found that those who reported greater breast health knowledge, were more likely to participate in sport and exercise - so by informing and empowering women, we can help improve physical activity levels (6).

Affect on performance

You may be lucky enough to not be affected by one of the previously mentioned factors - but have you considered the impact of your breasts on performance? For women involved in competitive sports, it is in your interest to listen to this next part as research suggests that your sports bra may impact how you perform, including how efficiently you run and even how you breathe (7). And it makes sense right? One of the cardinal signs of a pain or an injury is immobilisation - for example, if you hurt your leg, you will limp to reduce the amount of pain experienced. If your breasts start to cause discomfort when you run, you’re likely to change how you run and how you breathe, to try reduce breast bounce and offset some of that pain. Personally I don’t like running in the days leading up to my period when my breasts are most tender - and you will never find me doing a burpee during this time either. Research into whether the breast can negatively have an effect on performance is in its infancy but watch this space.

72% of females have reported exercise-induced breast pain (1). Over a third of female runners surveyed at the 2012 London marathon reported breast pain - with 17% reported it affected their participation (2).

Finding the right sports bra

When it comes to choosing the right sports bra for you, there are 3 main things to consider:
Function - Is the sports bra suitable for the type and intensity of your activity?
Fit - does it fit your body? 
Comfort - is it comfortable to wear?

Function - High, medium, and low impact support 

Sports bras are mostly grouped into high, medium, or low impact based on the support they offer and type of exercise they are suitable for (i.e. low impact and yoga or high impact and running). While this classification is useful when it comes to picking the right sports bra,  little is known about how levels are scientifically informed and they can be hugely variable from brand to brand (7). A recent review investigated 98 sports bras and found that 82%, 45%, and 69% of sports bras brand-classified as low, medium, and high support , respectively based on the reduction of breast movement they offered (8) . I’m not saying this is not a useful classification but I encourage you to inspect the sports bra further with the following pieces of advice before securing the deal. 

Most of the support from your sports bra should actually come from the under band, with only a small amount of support coming from the shoulder straps to reduce pressure on the shoulders.

Key Features of sports bras

There are a number of features of sports bras that contribute to performance including; bra style, shoulder strap adjustability and configuration, cup padding, underband adjustability and closure type, presence of an underwire, type of material, and neck line (to name a few!).

Under band 

You might be surprised to hear that most of the support should actually come from the under band with only a small amount of support coming from the shoulder straps to reduce pressure on the shoulders. An adjustable under band is advised for greatest comfort and reduction in breast movement (7,8,11,12). The fastener type (e.g. zip or hook and eye) should use non abrasive materials or should be covered to prevent abrasions to the skin (11). Bras that open at the front or back may also be easier to put on and take off for women with larger breasts or restricted shoulder mobility. 

When checking the fit of the underbrand, it should feel secure to fit without pinching the skin. For a quick test, raise your arms when you’re trying it on and check that it does not ride upwards. 

Shoulder straps 

Shoulder straps come in various orientations, the most classic types are vertical/straight, cross-strap, or racerback. Strap orientation is a personal preference, and similar pressures are generated at the bra strap–shoulder interface during running, irrespective of orientation - assuming if the straps are properly fitted (11,13). That said, non-vertical straps can help prevent the straps slipping off the shoulders (11,14). But on the flip side, In terms of comfort, a wide, padded vertical strap appears to be preferable for women with larger breasts (13). 

Ideally shoulder straps should be adjustable to accommodate for different torso length and breast positions. Sports bras that are not adjustable are more likely to stretch overtime and so not suitable for high impact activity where bounce is likely to occur.  When adjusting your straps, it is important to ensure that they are comfortable and not digging in (i.e., too tight) or sliding off (i.e., too loose) your shoulders (11). 

When it comes to tightening bra straps, realize the slide adjusters may not align and that each strap may be a different length. Keep in mind that most of the female population have asymmetrical breast sizes, with the left often larger than the right (15) . This is one reason why it is important that sports bras allow both underband and strap adjustment to facilitate individual breast support. 


Cups can have various features such as padding, underwire, panels, seams (7). Cups with padding can protect the breasts in sport and also provide additional support to the breasts (16). The cups, or front panel in a crop top, should completely cover or encase each breast. The breast should not bulge over the cup or neckline (a sign it’s too small) nor should there be wrinkles or gaping ( a sign it’s too big). The gore (bit between the cups) should sit flat on the breast bone (not on your breast tissue), if this is floating away from your chest, either the cups may be too small, or the underband too big. Not all bras have an underwire, but if it does, it must fit the shape of the breasts correctly and lay against the rib cage (not on the breast tissue) (11).


In general, the higher the neckline, the more supportive the bra - for every 1cm increase bounce reduction increases by 0.75% (8). Additionally, the side panel of the sports bra (under your armpit) must be wide enough to completely cover your breast tissue to stop side-to-side movement  - but it should not be too high as it may cause chaffing (11).

We must remember that the breast tissue extends all the way up to the collarbones and also up into the armpit. 

Cups can have various features such as padding, underwire, panels, seams (7). Cups with padding can protect the breasts in sport and also provide additional support to the breasts (16).

Takeaway message

I really hope you feel slightly more informed and confident about choosing your next sports bra. I will emphasise though that at the end of the day, you can have the best, most scientifically-informed sports bra but if it doesn’t fit you properly, it’s not going to be effective in supporting you or your training. So my top tip? When trying it on, first make sure to adjust it accordingly to fit your body and then do a few star jumps to see how secure it feels. You wouldn’t just buy a shoe without trying it on and taking a few steps in it right?


  1. Gehlsen G, Albohm M. Evaluation of sports bras. The Physician and sportsmedicine. 1980 Oct 1;8(10):88-97
  2.  Brown N, White J, Brasher A, Scurr J. The experience of breast pain (mastalgia) in female runners of the 2012 London Marathon and its effect on exercise behaviour. British journal of sports medicine. 2014 Feb 1;48(4):320-5.
  3. Mason, B. R., Page, K.-A., & Fallon, K. (1999). An analysis of movement and discomfort of the female breast during exercise and the effects of breast support in three cases. Journal of Science and Medicine in Sport, 2(2), 134–144. doi:10.1016/s1440-2440(99)80193-5 
  4. Scurr JC, White JL, Hedger W. Supported and unsupported breast displacement in three dimensions across treadmill activity levels. Journal of sports sciences. 2011 Jan 1;29(1):55-61.
  5. Bridgman C, Scurr J, White J, Hedger W, Galbraith H. Three-dimensional kinematics of the breast during a two-step star jump. Journal of Applied Biomechanics. 2010 Nov 1;26(4):465-72.
  6. Burnett E, White J, Scurr J. The influence of the breast on physical activity participation in females. Journal of Physical Activity and Health. 2015 Apr 1;12(4):588-94.
  7. Forsyth J, Roberts CM, editors. The exercising female: science and its application. Routledge; 2018 Sep 28.
  8. Norris M, Blackmore T, Horler B, Wakefield-Scurr J. How the characteristics of sports bras affect their performance. Ergonomics. 2020 Oct 14:1-6.
  9. Page KA, Steele JR. Breast motion and sports brassiere design. Sports Medicine. 1999 Apr;27(4):205-11.
  10. McGhee DE, Steele JR. Breast elevation and compression decrease exercise-induced breast discomfort. Medicine and science in sports and exercise. 2010 Jul 1;42(7):1333-8.
  11. McGhee DE, Steele JR. Biomechanics of Breast Support for Active Women. Exercise and sport sciences reviews. 2020 Jul 1;48(3):99-109.
  12. Bowles KA, Steele JR, Munro BJ. Features of sports bras that deter their use by Australian women. Journal of Science and Medicine in Sport. 2012 May 1;15(3):195-200
  13. Coltman CE, McGhee DE, Steele JR. Bra strap orientations and designs to minimise bra strap discomfort and pressure during sport and exercise in women with large breasts. Sports medicine-open. 2015 Dec 1;1(1):21
  14. Bowles KA, Steele JR. Effects of strap cushions and strap orientation on comfort and sports bra performance. Medicine and science in sports and exercise. 2013 Jun 1;45(6):1113-9.
  15.  Exell TA, Milligan A, Burbage J, Risius D, Sanchez A, Horler B, Mills C, Wakefield-Scurr J. There are two sides to every story: implications of asymmetry on breast support requirements for sports bra manufacturers. Sports biomechanics. 2019 Jun 16:1-3.
  16.  Parthasarathi D.V, Priya, T.R, Sivaranjani, S., & Dhivya., A (2016). Design and development of sports intimate apparel: A review. International Journal Online of Sports Technology and Human Engineering, 3, 1-9


How do you know if your sports bra is too small?

A sports bra should fit so that you feel supported but restricted. Sports bra sizing should be snug but not restrict your breathing or movement pattern. The right sports bra size is essential for breast support and comfort.

How do you know if a sports bra fits?

Your sports bra should feel snug but not too tight around your chest. It should enable you to breathe easily and should cover all of your breast tissue for maximal support and function. 

Should you size up in a sports bra?

Sports bra sizing is definitely a tighter fit than normal bras but you should not size up because of this. The sports bra is designed to provide more support and therefore it is necessary it feel tighter. The bra is supposed to feel more snug than normal but still comfortable.