Running, lifting, and moving more, can cause more jiggle and swing, if you know what I mean. I was that girl -- I layered up several bras, with still no prevail in getting the support I needed and wanted. Finding a good sports bra is much easier than you think. There are sports bras out there that do more than just give you an impressive uniboob.
Now, here's the sports bra that saved my cardio and weightlifting life...
I bought this sports bra about 4 years ago. I still wear it. You can find this bra on Amazon or on their direct website, movingcomfort.com. It was the best $50 I had ever spent.
This bra is so supportive, I actually even wear it under everyday clothes, because it gives me better support than my regular bras. It's definitely worth investing in a great sports bra.