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80% of women wear the wrong bra size, but it doesn’t have to be this way. From support, to fitting and construction – here’s what you need to know to pick the best sports bra for you...

Why is it important to have a good sports bra for running?

The unique motion of running causes your breasts to move in a figure of eight motion, sometimes up and down as much eight inches. This puts your Cooper’s ligaments - the thin collections of connective tissues that help support your breasts - under huge strain. Without the correct support, you’re likely to experience soreness and could cause lasting damage.


Sports scientists from the University of Portsmouth studied how breast tissue is damaged when running, in regular bras and a variety of sports bras. They found low to medium impact sports bras reduce bounce but are not effective for restricting the side-to-side movement that occurs when running.


In fact, their research shows that women change the way they run depending on the type of bra worn. So not only will a good sports bra provide you with vital support, it could help you to set a new PB too.

What level of support do I need?

Sports bras offer three different levels of support: low, medium, and high impact. The type you need depends on your cup size and the type of exercise you do. 


Low impact activities: Walking, yoga, strength training.


Medium impact activities: Dancing, skiing, cycling.


Construction: Low-medium impact sports bras typically feature a cup-less design and restrict movement by compressing the breasts tightly against the chest wall. 


High impact activities: Running, aerobics, mountain biking.


Construction: High impact bras are made with a defined cup structure – akin to regular bras – to encapsulate and support each breast. Some high impact bras will use a combination of both encapsulation and compression methods to maximise support.

Sports bra fitting guide

Step 1: Rib cage measurement:  Measure around your rib cage, just beneath your breasts. The tape measure should be snug, but loose enough that you can fit two fingers underneath. Round down to the nearest full inch.


Step 2: Use the table below to find your corresponding band size based on your rib cage measurement.


Rib cage  Band size
25" - 27"
27" - 29"
29" - 31"
31" - 33"
33" - 35"
35" - 37"
37" - 39"
39" - 41"


Step 3: Bust measurement: Measure around the fullest part of your breast. Again, the tape measure should be snug but not so tight that it restricts breathing.


Step 4: Subtract your rib cage measurement from your bust measurement. The difference is your cup size. If you’re in between sizes, round up. 


Difference in cup size
 Your cup size
3 AA
4 A
5 B
6 C
7 D
8 DD
9 E


An alternative to steps 3 and 4: Try a few different cup sizes for fit. Cups should fit without gaps or wrinkles, they should feel snug and secure but shouldn’t be so tight that your breasts spill out the side or over the top of them.


Step 5: Use our size charts to identify the right size sports bra for you. 

Tips for getting the perfect fit

Even once you have you have your measurements, finding the right sports bra can be tricky and usually requires you to try a few different sizes and brands. Here are some tips for getting the perfect fit…


Snug, but not too tight: A sports bra should fit tighter than a regular bra but shouldn’t restrict breathing; you should be able to fit two fingers between the straps and your shoulders.


Wrinkles are bad: The fabric of the cup should be smooth. Wrinkles in the fabric are usually an indication that the cup is too big. Conversely, if you’re spilling out of the cup, it’s too small.


Watch out for gaps: Any underwire should lay flat against the rib case, below your breast tissue, and should not pinch or dig in.


Adjust the straps: Raise your hands up over your head. If the band rides up it’s usually a sign it’s too big, though it is possible that the straps or the back closure may need adjusting.


Move around: Before buying your bra, jump around and swing your arms – (it’s probably best to do this in the changing rooms or somewhere else other people can’t see you). If you experience pain or discomfort, then try another sports bra.


If in doubt, visit your nearest Runners Need store for a free bra fitting service.

How long does a sports bra last?

A sports bra will last around 30-40 washes, but the technical fabric will loosen with each cycle, making it less effective.


To give your bra a longer lifespan wash in cold water, avoid fabric softener and bleach, and do not tumble dry as heat will accelerate the elastic degradation. Instead, dry it flat and if your sports bra starts to rub or chafe invest in a new one. 

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