I am a bit confused about the arm bands that are sold for the iPhone. I am looking at protecting my iphone and I am looking at a Polycarbonate case at all times. I also need something to hold my phone while I am working out and was looking at arm bands but can't tell if they are designed for an iphone that is already in a Polycarbonate case, or do they expect you to remove the phone from the case before putting it in the arm band?