The Benefits of Running and Sports Bras

The benefits of a sports bra

Research into the area of sports bras and breast biomechanics is a relatively new field that has sparked interest in the past decade with more and more research being carried out to highlight the importance of wearing a good sports bra and what exactly comprises a good fit and level of support.

The breasts contain very minimal internal support consisting only of skin and the Cooper’s ligament. The lack of muscle in the breast results in breast motion during exercise. This can then lead to:

  • Exercise related breast pain
  • Breast ptosis (sagging)
  • Forces acting on the body which can affect sports performance
  • Psychological anxiety and insecurity.

These factors sometimes become a barrier to participation, which is why we emphasise the importance of each individual finding a sports bra that is both comfortable and supportive for their own shape and purpose.

There are 3 different types of sports bras: compression, encapsulation and combination.

  • Compression bras – compress the breast tissue towards the chest wall which decreases the force acting through the breast.
  • Encapsulation bras – on the other hand separate the breasts which results in the mass being halved as they move independently.
  • Combination bras – as the name suggests, use a combination of compression and encapsulation; moulded cups provide the encapsulation combined with a compressive layer. This does not make it twice as supportive as the others; they all work as effectively as each other but in different ways.

Generally speaking, you should be the same size in your sports bra as you would be in your everyday bra; however you will probably find that this varies a lot by manufacturer. This is because the manufacturers all use different size specifications.

The traditional tape measuring method was developed back in the 1930s and research at the University of Portsmouth has found that it can be inaccurate, as women’s bodies have changed drastically in the past 70 years. The traditional method involves two measurements: one from under the bust around the ribcage, and the other from around the fullest part of the bust. The first measurement gives the back size in inches, and the difference between the two measurements determines cup size; however it was only designed to go only up to a D-cup and half of women in the UK now exceed that size.


We offer a fitting service in store that has been developed by the world leaders in breast biomechanics research who are based at the University of Portsmouth. We start by getting you to try the size you would ordinarily purchase and then assess the fit using a five-step approach to see if that is the right size for you. We assess the length of the straps, the shape of the underwire (if present), how well the back fits, how well the cup fits and whether the front band is in contact with the breastbone.

  • Strap length: You don’t necessarily need to adjust your straps to the same length on each side. Many of us have sloping shoulders, perhaps from carrying bags around on one side for years, so you may find that one strap needs to be tighter than the other. We look for no more than an inch of give in each strap.
  • Underwire shape: If you press on the underwire of your bra, it should press on bone, not breast tissue. The underwire should sit on your ribcage, encasing your breasts but not digging into them.
  • Back fit: You should just be able to fit two fingers under the band. It should feel snug (potentially tighter than you’re used to) but not uncomfortable. If it rides up in the middle of your back, the band is too big and won’t give you enough support.
  • Cup fit: There should not be any breast tissue spilling out the top of the cup; this indicates that the cup is too small. Similarly, there shouldn’t be any wrinkling in the material as this suggests that the cup is too big.
  • Front band: The middle should sit flat against the breastbone. If it’s pulling away, leaving a gap between the middle of the bra and the skin, the cup size is too small.

If one of these 5 areas doesn’t fit quite right we will adjust the size using the bra fit cross grade chart below. For example, if a 34D is too loose on the band, the next size to try would be a 32DD to account for total volume.


When choosing the right sports bra, consider the activity you are going to be using it for. If for example you are going to be jogging, try running on the spot to test the supportiveness. We advocate the same approach with sports bras as we do with footwear: try a few different styles on and see what is the most comfortable for you. They will all do the same job, but you need to find one that is suited to your shape and activity.

To view our full range of sports bras,

Shop Sports Bras
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