A really good bra for running is comfortable and supportive. Sports bras come in medium support (lighter-weight fabric and for smaller-breasted women), high support (for average-size breasts), and maximum support (they have more construction to them). When trying them on, jog in place in the change room. Does the bra feel like it's providing the support you want? Also, sit down and take a deep breath. If it feels restrictive, it's too small. Here are three options (prices listed are for Running Room stores across Canada).