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The Construction of Sports Bras

Sports bras are a different breed of clothing. Their fabric and construction are completely unique and their expected level of performance is like no other clothing. They’re expected to keep our girls in place so that they don’t bother or bounce around during our workouts yet they’re suppose to be breathable, flexible, and comfortable. To be honest, I don’t think I could or will ever make a sports bra. This past year, I visited factories and saw first-hand the machines that created this category of clothing and never ever would I want such machine in my apartment. They’re loud, huge, and kind of scary looking. I’m not saying they can’t be made my home sewers, because they can (click here to see how Melissa of Fehr Trade made her own running vest and leggings), I’m saying I hesitate to dive into the category. Regardless, I think the technology is really cool and interesting to know and I wanted to share my knowledge of the category with you. Enjoy my loves…

Fabric: The fabric of sports bras and all other active wear is what sets this category of clothing apart from every day wear. I’m sorry if my next bit gets a tad bit technical but the technology is quite amazing and I promise that if you follow along and read slowly, it will all make sense.

As opposed to the fabric of every day wear (cotton, wool, linen), the fabric of active wear has one main purpose – to move moisture from the skin, through the fabric, and to the outside air (this process is called wicking) in order to cool down the wearer. What’s interesting about this is that most active wear, including sports bras, are made of polyester, nylon, lycra, or spandex or a blend of the previous four with cotton yet polyester, nylon, lycra, and spandex (not cotton) are hydrophobic by nature, meaning they don’t absorb water easily. So how can a hydrophobic fabric move moisture away from the body? Well, by modifying the composition and structure of the fiber while it is being manufactured (because polyester, nylon, lycra, and spandex are manufactured fibers/fabrics), they are able to transport the moisture from the wearer’s body to the outside air, and thus, keep the wearer cool during workouts.

So how does the fiber or fabric change during manufacturing that allows it to wick? I’m so glad you asked. Moisture is moved from the wearer to the outside air through the tiny spaces between the fibers. The teeny tiny spaces form just as small passageways, called capillaries, that move moisture away from the body. The narrower the capillaries, the more effective the transportation of moisture. So, the fabrics of sports bras and all other active wear have been modified to have more and narrower capillaries. Simple, right?

Today, the best fabric for wicking is a called COOLMAX. It is trademarked by INVISTA and you will know that a sports bra or another piece of active wear is made of this fabric because the content label will actually state the trademark name COOLMAX (as opposed to just saying polyester, nylon, lycra, or spandex). The next best fabric for wicking is another trademarked fabric called SUPPLEX. It’s not as good as COOLMAX but is still does a damn good job wicking.

Cotton is also used in sports bras but is almost always used as a blend with nylon, polyester, lycra, or spandex. Cotton, by nature, is a hydrophilic fiber, meaning it attracts water but it also retains water. For everyday wear, this is okay, but for active wear, this is not okay. The wearers wants to get rid of the moisture he or she is sweating, not retain it. Cotton is also used in blends to provide a softer hand.

Mesh is also used in active wear for breathability. I have noticed that many of my sports bras are lined with mesh and the middle section of the racer back as well as the cleavage area have mesh to allow air to pass through.

Construction: Sports bras are almost always and pretty much solely sewn with coverstitches and chainstitches. As with normal bras, a straight stitch cannot be used to sew sports bras because it would break as we moved vigorously, and many times wildly, throughout working out. Although zigzag stitches provide give to a seam, it still isn’t enough to withstand a workout.

The seams of sports bras are also almost always and pretty much solely overlapping (as opposed to placing right sides together and sewing) and many times coverstitches straddle the seam (see sketch). The reason for this type of seam construction is used to reduce bulk.

Silhouette: There are types of silhouettes of sports bras – compression, encapsulated, and underwire.

Compression, just like its name, compresses the chest to provide support and keep the girls in place. These bras usually don’t have seams, the only exception being a side seam, and is best for the smaller busted girls (A-cup and maybe B-cup).

The second type of silhouette, the encapsulated, provides more support than the compression with the use of seams that shape larger busts (B-cup and bigger). Although the seams can be a princess seam shape, they are usually in the shape of a bra cup. Also, binding is top applied on the inside and straddles the cup seam. The purpose of the binding is to act as an underwire but with less rigidity.

The third type of silhouette, the underwire, is for the largest of girls (C-cup and larger ((although B-cups can wear them if they want more support)) ). This type of bra is basically a normal bra but made with activewear fabric.

All three silhouettes of sports bras can be made as a racer back or with two straps (one left and one right). The racer back provides the most support.

Band: Just as with normal bras, the wider the band, the more support provided.

Closure: Sports bras usually have no closure and are a pull-on type of clothing. The reason is closures can be very irritating during a work out (hooks and eyes = ouch!). If sports bras have a closure, it is usually in the form of a hook and eye and it is in the back of the bra, not the front.

When to throw away: Just as a rule of thumb, if you wear your sport bra 3-4 times a week, it should be thrown away/replaced every six months. The reason for this is the elastic looses elasticity and retention and doesn’t provide support is used to.


  1. Reply


    very interesting – thank you!

    It would be so cool to be able to sew my own sports bras. Do you happen to know – is Coolmax available to buy by the yard somewhere??

    • Reply


      You asked a good question and at first, I didn’t know. So I did a little research (via Google – Google knows all) and found that many places require a minimum of 100 – 500+ in order to buy the fabric but Ebay had a couple sellers that sold by the yard. Below is a link to one of the sellers I found. I hope this helps 🙂


      • Reply


        thank you!

        PS I don’t know if it’s just me, but those confirmation letter that need to be entered when posting a comment are so hard to read.

        • Reply


          I know they are and that is the point. I hate them too but it prevents from spammers. If I don’t have it, I receive literally 100 spam comments (at least) a day.

          • Fleur

            This helped me so much with Fashion and Design! Thank you 🙂 xx

  2. Reply

    Daughter Fish

    Maddie, I love this post! And the rest of your bra posts here! I’ve long wanted to recreate my favorite yoga top, but have felt really confused about the proper mesh to use inside for the built-in bra. It feels like you’ve revealed some top secrets here that I’ve never been able to pry from the locals in my garment district (NYC). Looking forward to reading more posts, and I’m definitely linking this entry to my tank with a built-in bra post!

    • Reply


      Thanks love. I too am like you in that I’m very hesitant to make any type of activewear. I’m interested to see how yours will turn out. I’ll just have to stay tuned 😉

  3. Reply


    Thanks for the link! I just wanted to chime in about why cotton isn’t highly regarded for sportswear, and why others like me actually AVOID buying any running gear that contains it. In short, cotton = chafing. You know when you see those photos of marathon runners with bleeding nipples? They’re nearly always wearing (cotton) teeshirts. And the easiest way to avoid foot blisters is to wear 100% polyester running socks (and lather on the Body Glide!).

    Believe me, in normal sewing, I shun polyester and tend to only sew with natural fibres, but for exercise wear, polyester is KING.

    Thanks for explaining the whole wicking process – I wasn’t entirely certain how it worked before.

    • Reply


      I never knew that 100% cotton caused chaffing. Always something new to learn. Thanks!

  4. Reply


    I was really looking forward to reading this post! Fascinating topic and thanks for all the intel! Awhile back I went a-looking for Supplex and the good smooth-feeling stuff is hard or impossible to find. For workouts I wear mostly yoga-style sports tops that have built in bras (and I can get away with them as I’m small), but the thing I want to recreate and of course can’t at home w/o some crazy machine is the lapped/butted seam that’s in a lot of especially the bottoms (and sometimes the tops). It’s so smooth, it doesn’t chafe. But now I’m going to admit my guilt in keeping these things around for much, much longer than 6 months. 😉

  5. Reply

    Phung Nervis

    Touche. Great arguments. Keep up the amazing work.

  6. Reply


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  10. Reply


    Thank you, this has been so helpful for my assignment. I study Fashion Management and Marketing, so the business side of fashion and I have a big interest in sports bras therefore using it for my project but as we don’t have a design unit in my course, I have struggled a little bit in knowing the right information for making of sports bras, so thanks a lot!

    • Reply

      Maddie Flanigan

      I’m so glad that this helped you 🙂

    • Reply


      Hi Susie. Have you finished your sports bra project and how did it turn out? I am in the process of finding someone to make a sport bra prototype for me from scratch and I am having a very hard time here in Memphis, tn. Any advice? Thanks in advance;)

  11. Reply

    Payal Parija

    Very helpfull 🙂

  12. Reply

    Shikha Gautam

    nice info

  13. Reply


    Nice information, but plenty of sports bras offer rear closures. They are pretty necessary for anyone on the top heavy side.

  14. Reply


    What a fab blog! Can you provide details of any of the factories that you have visited that make sports bras? Thank you!!

    • Reply


      Hi Zoe, were you able to locate any companies that make sports bras? I have come up with a new type of sports bra and am looking for a company to make me a prototype. Any suggestions? Thank you

  15. Reply


    How much fabric do you need to actually make the sports bra? I’m trying to figure out how many yards of fabric are necessary for an entrepreneurship project I’m doing for class. Please help!

  16. Reply


    Sammy, depending on the size you’re sewing, you can usually make 2-3 bras from 1 yard of fabric. Hope that helps!

  17. Reply


    Which sports brands are using COOLMAX and supplex???

    Plz guide

    • Reply

      Jenn v

      Lululemon’s fabric, for the pants at least, is Supplex. You can buy it from a place in NYC called Spandexworld.com. It’s not identical but it has the same hand.
      I’ve been experimenting with activewear too, and there are lots of new patterns at Jalie.com and technical fabric is easily sourced online. 🙂

  18. Reply


    Hi Maddie! Great blog. I have a business inquiry and was wondering what the best way to get a hold of you would be?

    • Reply


      Hi Caroline, were you able to get in touch with Maddie? If so, could you let me know the best way to reach her for a sports bra project I’m presently working on? Thank you

  19. Reply

    Babs King

    Hi there! I am wondering if the straps here are made with a foldover elastic? Or is it the same fabric as the bra itself? Thanks!

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