For most of my life, my requirements for a sports bra were purely aesthetic. Small chest, no real support needs — I'd buy the cutest one on sale, never think about the features, and run 10k in a yoga bralette without batting an eyelid.
Now I'm a breastfeeding mum, and that $19 bralette no longer supports a thing.
I've been trying to get back into running postpartum, strapped on one of my old favourites, and knew within three strides that my small boob club membership had been revoked.
A few years ago I attended the Women in Sports Congress, where I heard Professor Deirdre McGhee — director of Breast Research Australia — speak, and walked out thinking: I had no idea there was this much science behind sports bras, or that getting it right could actually make you run faster. I filed it away and mostly forgot about it. Until now.
What also gets me is that women are still largely dependent on shop assistants to fit their sports bras, when there's actual research telling us exactly what to look for and how to check it ourselves. Here's the TL;DR:
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in this article
the sports bra lore you were never given
I've never really thought about this way before, but isn't it funny that we happily drop $200 on running shoes, but we treat our sports bras like cute accessories. Which is crazy when you think about the anatomy of our breasts, which are made up of of tissue and fat, supported by skin and Cooper's ligaments only and no muscle.
According to Sports Medicine Australia, during one hour of running bounce approximately 10,000 times. It's no wonder that without proper support that repetitive strain causes pain and impacts performance. Research shows that a high-support, correctly fitted bra improves running efficiency, alters your upper body tension/posture, impacts your breathing patterns and landing biomechanics when your run.
the 411 on sports bra types
I always assumed sports bras were just sports bras. Turns out there's three different types.
Compression (crop top style) works by pressing both breasts against the chest wall as a single unit. Great for smaller cups and low-impact activity. The limitation is no separation, and straps are usually fixed — so if you need more support, you can't dial it in.
Encapsulation looks more like a regular bra, with defined cups that contain each breast separately. Adjustable bands and straps let you actually fit it properly. These are better for reducing movement by lifting rather than just squashing.
Hybrid combines both — defined cups plus compression over the top. Adjustable everything. This is what you want for high-impact running, especially if you're a D cup or above.
the 4-step fit check to find the one you need
I always assumed the straps did the heavy lifting (aka the support), but it turns out they're don’t, and it's actually the band that should provide most of the support. If you're relying on straps to hoist everything up, you're probably just giving yourself shoulder pain.
#1 the band: It should feel firm around your ribcage. Raise your arms straight up. If the band slides up or you can pull it away from your body easily, it's too big.
#2 the cups: Scoop all your tissue in. If the fabric wrinkles, it's too big. If anything's spilling out at the front or toward your armpit, it's too small. High necklines help contain everything.
#3 the straps: They should feel firm on your shoulders and shouldn't slide off (too loose) or dig in (too tight).
#4 underwire: Should sit flat against your breastbone and flat on your ribs near your armpit. If the wire is resting on breast tissue anywhere, it's the wrong shape for you personally. And for anyone breastfeeding: rigid underwires can cause blocked ducts so it's best to stick to wireless or hybrid styles.
the "two-bra" hack
If you’ve tried everything and still feel too much movement, you aren't alone. The SMA explicitly notes that athletes with larger breasts (D+) often need to wear two bras simultaneously to achieve adequate support.
This doesn't mean wearing two old, stretched-out bras. It usually means layering a high-support encapsulation or hybrid bra underneath a sports bra crop top. Think of it as locking everything down with a base layer of separation, then adding a compression layer on top for stability.
yes, your sports bra has an expiration date
As a professional in this space, I probably shouldn’t admit that I’m still wearing sports bras from 2016. Because just like running shoes, it turns out sports bras have a "use by date".
Research shows many women wear bras where the elastic has become overstretched and the material worn out. If the band fits loosely or the straps no longer hold firm, the technical support is gone, and the bra should be replaced .
A final PSA on age: as we get older, the elasticity of our skin and ligaments decreases, meaning we actually require more support than we used to. If your old faves aren't working anymore, it might not just be the elastic—it might be that your body's needs have evolved.
