Snag the right support

Sure, your yoga sports bras works great for downward dog—but when it comes to running, you'll need one that's designed to lock them in for all that pavement pounding. So what should you look for? "The best sports bras are loose around the chest so you can expand your ribs and diaphragm more effectively. But they should also be form-fitting," says Deena Kastor, an American marathon record holder and 2004 Olympic marathon bronze medalist. Just make sure the cup is made of comfy material (like a soft compression fabric; look for descriptions that include the terms "breathability" and "compression")—you don't want to be itching at mile two!