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Tomima Talks: Get Scared Straight into the Right Sports Bra

There’s a very popular public trail near my home that I like to frequent for a couple reasons; few streets to cross, and great people-watching.  The woman walking her dog in heels.  The older male biker covered in spandex.  The cute couple in premeditated coordinates.  But, all too often I also see a buxom beauty bouncing along without proper breast support. Not only do I think “ouch!” but I cringe at the fact that she must not know the long-term irreversible damage she is creating to the shape of her breasts. Whatever your cup size, a woman’s goal during any kind of work-out activity should be to make sure her breasts move in unison with the rest of her body.  Breasts should not be bouncing independently from the body (e.g.: moving up while the rest of your body is moving down), nor should they have a “catch up” delay with your body’s movements. You wouldn’t go running in flip flops, would you?  Here are the many reasons why a good sports bra is as important to your workout as your footwear.

Breast Composition

A quick anatomy lesson about breasts.  They are mostly glandular tissue that rest in front of your pectoral muscles and are kept in place with skin and internal ligaments known as Cooper’s ligaments. As we age, our skin tends to thin and lose elasticity, so our primary breast covering loses firmness.  The internal Cooper’s ligaments are more like rubber bands.  Testing has shown that these ligaments can initially stretch about 3/4 inch during a short run.  Continual breast bounce tugging over time will cause these ligaments to lengthen. So, skin and ligaments are the two factors in breast sag.

Breast Movement while running.

You may be shocked to learn that sports bras only entered the market late in the 1970’s.  Women were participating in the Olympics starting in the early 1900’s. I will argue that it is the invention of the sports bra that catapulted higher numbers of women into sports participation – especially track and field events. Research has shown that a woman wearing a sports bra will reduce her pectoral muscle usage by 55%, thus reducing her fatigue while running. She can now run longer and faster if her breasts are one with her body movements. Proper breast support during exercise can also improve breathing rates and lung capacity which leads to improved thermoregulation. Breast pain during physical activity due to breast bounce is a well-documented complaint with 72% of exercising females making this claim.

Back in March of 2008, I found the one and only person studying the mechanics of breast movement on women while running.  In 2005, Dr. Joanna Scurr at the University of Portsmouth in Hampshire, England began collecting what is now 15 years of data on the subject.  At the time, she and I had a fascinating conversation about her preliminary findings. First, breasts move in 3 directions.  The graph on the left shows they move up and down, sideways, and also in and out on a woman’s chest. 50% of a breast’s movement is vertical, 25% is side-to-side, and 25% is in and out (the X-axis in the image on the left). At the time, she had tested twenty D cup-sized women ranging from 32D to 36D and had measured at least one bare breast having a 6” (15.4 cm) total swing while running.

Without proper support, all breasts are moving significantly. Of course, the size of the swing grows with breast size.  Physiotherapist Deirdre McGhee, Ph.D. a researcher with Breast Research Australia at the University of Wollongong found that the average 38D bare breast bounces vertically by about 5 inches during running while smaller breasts bounce around 3 inches, which can still be uncomfortable.  This explains yet again why 72% of exercising females claim to have breast pain during physical activity.

A follow-up breast bounce study published in the Textile Research Journal in 2012 further studied multiple breast points to determine where the greatest movement occurred. They first established 6 points on a bare breast (shown below on the left) and tested subjects aged from 24 to 40 with breast sizes from 34B to 38D. The graph below on the right represents the 3D movement.  The research found that the breast movement at all 6 points move in a shape similar to a pair of closing butterfly wings.

The greatest breast movement was at the apex (M4) and outer side of the breast (M3), and the greatest vertical breast movement came from under the breast (M2). Not surprising, as the breast size increased, the breast’s up/down movement gained inertia. So, the larger the breasts, the greater the stress and higher the pain from movement.  For me, the most interesting detail in all this research was what was happening in the M2 area of the breast – directly below the nipple.  Most women understand that we need to protect our breasts from the downward movement in a bouncing breast. But, equally, if not more important is also controlling the upward bounce movement.  The upward momentum stretches and ultimately lengthens our underbust tissue.  Left unchecked, underbust tissue lengthens allowing the breast mass to hang further down our chest reshaping and repositioning the direction of our nipple-areola complex. Therefore, a critical sports bra feature should also be a high rigid neckline to prevent upper breast bounce.

Best Sports Bra Features

The conclusion to all of this is that you need a sports bra that totally contains your breasts so that all of you is moving in unison.  A compression-style sports bra (think ACE bandage) is not as effective as a bra with complete, firm breast encapsulation. Side support panels along the sides of a sports bra’s cups reduce side-to-side horizontal breast movement.  Rigid fabric in the bottom of the cup reduces downward movement.  A high neckline with full upper-breast coverage in non-stretch fabric reduces upward breast movement. Cups that give you 360 coverage around your breast without stretching prevents the in and out breast movement on your chest. Wide straps that are more centered above the apex of the breast further stabilize your breast mass and reduce shoulder strain. Back in 2008 after my discussions with Dr. Scurr, My team and I started adding “Bounce Test” videos to all our High impact sports bras to give you our customers a sense of breast bounce.

Below are some examples of sports bras HerRoom offers with these features.  They are all displayed in white so you can clearly see their design differences, but all come in fabulous colors and patterns.

I hope this Tomima Talk helps you understand the importance of the right sports bra.  It is as essential as your workout shoes to optimizing your workout. Oh, and when you buy new shoes, you should also buy a new sports bra – both have been proven to need replacing at the same time.


Tomima Founder, Owner, & CEO


The right bra can change the way you feel about everything. Find the right style and fit in just a few minutes with our exclusive Bra Fit Quiz.

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