Oh, sports bras. I had a request for a sports bra post.
Sports bras are a world of their own. Many even use a S/M/L sizing. And it's very hard to find sports bras for anything higher than a DD cup.
There are 2 kinds of sports bras. I have both. Both kinds use compression to control breast movement. It's how the approach compression that makes them different.
A Compression bra is what we usually think of, the one that gives the horrid uni-boob look and just smooshes everything down. Compression has it's place when done correctly. One company I highly recommend that uses this is Enell. I wear an Enell bra for running. It's not the prettiest, but I don't care much about pretty when I'm working out. I just want to lose the bounce.
The other type is an Encapsulated bra. This means each breast is compressed separately. You'll see this much more in the higher cup sizes, and often with an underwire. (Underwires in sports bras are personal preference. I personally refuse to have an underwire in my sports bra.) My encapsulated sports bra is from Freya Active. Some "encapsulated" bras really make you wonder if they are truly working with your breasts individually, or just trying to have less of a uni-boob look.
As for sizing and fit, this is where sports bras are special. A sports bra just fits differently. The band should definitely be snug, but not to the point of pinching or cutting off blood flow. The cup(s) should firmly hold your breasts. You may find that you have to go up a band size in some sports bras, because companies know the bra should fit snuggly (and make them too snug). I actually tend to get compression bras a cup size or two smaller than I measure, which really smooshes those puppies down. I'm comfortable doing this, but I wouldn't recommend it for everyone.
When shopping for sports bras, you first need to think about what activities you want the bra for. I use my Freya Active for walking, bike riding, and other low-impact activities. My Enell is for running and other high impact activities. Just like the activity, your sports bra is low, medium, or high impact. Low impact means it won't give as much support and bounce-reduction, while high impact means lots of support and bounce-reduction. You may find it easier to have different sports bras for different activities, like I did. Some bras won't specify their impact level, but take a good look at the material and structure, and I bet you can figure it out.
So try on a sports bra, and once it's on, jump around, move around, bend, twist, go crazy in that dressing room. If you want to run in your bra, run in place. If you want to do yoga, do a few moves (and make sure you don't fall out).
Another aspect of sports bras is their lack of adjustability. (Is that a word? I'll have to look it up.) As I'm sure you know, most sports bras we know are a pull-on style. There are more and more styles now that offer adjustable straps or even adjustable hook closures. This is another reason to TRY IT ON. Make sure it's going to fit before you drop the money.
As for brands and where to shop? Hell, they're everywhere! I've heard good things about the Champion sports bras at Target for women up to a DD cup. I have shopped in a Title Nine store and found decent bras at good prices. Title Nine also has barbell ratings for their bras, to tell you their impact rating, and has more options for bigger chests. There are lots of places to find sports bras. You'll find lycra/cotton blends, bras with molded cups, moisture wicking, and all kinds of new techy things in today's sports bras. You have to find what works for you.
I hope this helps. Sports bras can be tricky. I'm currently debating whether to get another Enell or try the ShockAbsorber brand, which I would have to order online.