One of my most frequently asked questions is definitely “where can I buy fabric for yoga/running/exercise/etc?”, so I thought it’s high time I make an attempt at something like a global list.
In general, though, the word you should be searching for is “Supplex”. This is a brand name, though, like Lycra (whose generic term is “spandex”), but the generic alternative is something like “wicking spandex”, and generally isn’t used as often as “Supplex” in fabric stores, I’ve found.
If you can buy supplex at a decent price, buy it. It’s soft, has great recovery, wicks away moisture while you’re sweating, and stands up to washing without a ton of pilling. It can be hard to find though, and sometimes only comes in a limited amount of colours, but I wouldn’t hesitate to run a marathon in supplex – it’s great stuff.
If you’re running shorter distances, or in cooler weather, you can get away with exercising in any number of lycra/spandex jerseys, though. These won’t wick sweat away, but they come in a gazillion colours and prints, plus have a multitude of foil and sequin effects, and can be way cheaper, too. Ditto goes for swimsuit fabrics – you can certainly use them for shorter exercise sessions even though they’re not wicking. Personally, I wouldn’t mind running a half marathon on a cool day in lycra leggings, but your mileage may vary (pun intended!).