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What is a sports bra?

Why do the              
breasts move? 

There are no muscles in the breasts. The breasts are made of fat and glandular tissue, they sit above the pectoral muscles, but are unlikely to be directly connected.

Breasts have two weak supporting structures; the skin and the Cooper’s ligaments.

These structures are fairly weak, making the breast highly deformable (that means it moves). 

Why do I need a good sports bra?

If the breasts are not properly supported in sport, breast movement is likely to be considerable; we have reported up to 19 cm of breast movement during jumping jacks!

Breasts can accelerate faster than an F1 car if not properly supported during sport. 

Excessive breast movement has the potential to cause breast pain and may be even tissue damage.

Movement related breast pain is reported to affect up to ~half of exercising women (51% of female Tokyo Olympic athletes reported experiencing breast pain)

Breast movement exerts a load/force on the supporting structures of the breasts and exerts a load on the body.  These forces may negatively affect sporting performance. Many women experience skin friction issues due to poor bra choices during sport.

What might happen  to my performance if I don't wear a good sports bra?

Excessive breast movement has been linked to increases in muscle activity, increases in torso, pelvis and arm movement, increases in breathing frequency, we have also reported a 4 cm increase in stride length as breast movement increased. A 4 cm increase in stride length over a marathon distance equates to a mile!


It has also been reported that excessive breast movement can lead to reluctance to participate in sport, or even a drop out from sport.

What can we do about breast movement?

If we reduce breast movement we reduce breast pain, we reduce the risk of damaging the breast tissue and we may even improve performance or encourage participation.

So, we need appropriate breast support for the activity that we are doing.

What is a sports bra? 

The primary purpose of a sports bra should be to support the breast.  This means that a sports bra should reduce the movement of the breast by holding it in position when we exercise. 

How does a sports bra work?

Sports bras work to reduce the movement of the breast in two different ways; either they compress the breasts towards the chest (compression sports bras), or they encase, lift and hold each breast separately (encapsulation sports bras). 



Compression sports bras look like cropped tops and they contain little to no structuring inside the bra, this means they don’t have any cups.  You can tell if a bra is a pure compression crop top by turning it inside out, if it has no cups, no moulding, and no seaming to shape around the breasts, e.g. it just has a flat panel at the front, then it is likely to be a pure compression sports bra.  

These compression sports bras compress the breast tissue towards the chest, but the tissue doesn’t get smaller, instead, it redistributes itself. This means that when the breast tissue is compressed it has to go somewhere, therefore, compression sports bras tend to have more stretch to allow the breast tissue to move upwards, or outwards, or inwards, or everywhere. However, more stretch in a bra usually means less support. 

Compression sports bra

Compression sports bras often contain no fasteners (like a hook and eye), so the underband cannot be opened and closed. Instead, most of these bras are pulled on and off over your head and shoulders. 

This means that pull over the head bras have to have enough stretch to get them over your head and passed your shoulders (this is the tricky part). This sometimes means more stretch, particularly in the underband.  Remember the underband is a key component for support in any bra. Ideally, you want the underband to be firmly fitting and not too stretchy when it is in position. But having a tight/firm underband can make it really difficult to get the bra on and off over your head and shoulders.  Consequently, pull over the head sports bras usually have a slightly looser or more stretchy underband, meaning they often provide less support.  

Because compression sports bras contain some stretch, it is usually easier to find a good fit.  Compression sports bras usually come in a XS, S, M, L, XL size range, making it simple to select a size.  This does mean that if you have an unusually body shape or size, sometimes this sizing system might not work for you.

Top Tip: Because of the increased stretch, as a general rule, a pure compression sports bra (with no structured cups) is not recommended for anyone with a bra cup size above a C cup, because they may not provide the necessary support.

Encapsulation sports bras

The other way we can reduce the movement of the breasts is by encasing, lifting and holding each breast separately. Sports bras that work this way are called encapsulation sports bras.  They usually look a bit more like an everyday bra, for example they contain cups that separate the left and right breast. 

Rather than compressing the breast tissue, encapsulation sports bras work by lifting the breasts off the chest and holding them in place.


Because there is no compression required in an encapsulation sports bra, they usually contain much less stretch (if any) when compared to compression sports bras. This means that encapsulation sports bras tend to be stiffer bras, which can be more effective at reducing the movement of the breast (increasing support).  

Because encapsulation sports bras often have less stretch than compression sports bras, this makes it more important to get the fit right.  The lack of stretch in the cups means that you should be looking to match the cup volume (size) with the volume (size) of your breast.  This isn’t always easy! Whilst compression sports bras fit a lot of women (because they have built in stretch), encapsulation sports bras are harder to fit.  These types of sports bras tend to be offered in cup and band sizes, due to the importance of getting the fit right.   Encapsulation sports bras tend to offer more adjustability to help get the fit right, for example adjustable underbands and adjustable shoulder straps. 

Top Tip: As a general rule, if they fit well, encapsulation sports bras will provide superior breast support and are recommended for all bra sizes.

Combination or hybrid sports bras?

There are many sports bras available that contain a combination of compression and encapsulation. For example, they may look like a crop top on the outside, but when you turn them inside out you can see moulded or seamed cups to separate the breasts. These are called combination sports bras.  

Combination sports bras are a good compromise between compression and encapsulation sports bras. Combination sports bra contain some stretch, improving fit and some encapsulation, providing support to the breasts.  Research shows that combination sports bras can be just as effective as encapsulation sports bras.  

Combination sports bras are available in XS, S, M, L, XL sizing or in cup and band sizing depending on the brand. These sports bras also tend to be available with or without adjustability in the underband or shoulder straps. Some combination sports bras can be the pull over the head type and others have a fastener to allow you to open and close the underband, making them easier to get on and off, ensuring the underband is a good fit and doesn’t stretch out. 

My tips on what
 to look for in a sports bra


I always opt for a high support sports bra that doesn’t contain too much stretch and has some moulded or structured cups on the inside.

  • For a number of reasons, I always look for a sports bra with a fastener (one with an underband that can be opened and closed).

  • A fastener helps me get the bra on and off.

  • A fastener also means that the underband can be a bit firmer, this is reported to help with support.  

  • A fastener may also stop the underband stretching out over time. 

  • I don’t mind sports bras with an underwire, I find it helps with shaping. 

  • Remember padding in a sports bra is for modesty (nipple concealment), it doesn’t provide any breast protection. 

  • The bra industry reports that racerbacks are the most popular shoulder strap design for sports bras. Racerback shoulder straps will never slip off your shoulders. 

  • Moisture management is important for me to help reduce rubbing and chaffing, particularly in the summer.

  • Research shows that the higher the neckline of a sports bra the more support it provides.

  • Wide, padded shoulder straps are thought to reduce excessive pressure on the delicate tissue of the shoulders, although we need to do more research on this.

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