I'm sure you can relate to feeling a little uncomfortable when you're exercising hard — burning muscles, heavy breathing, and even itchy legs are normal. Sharp pain, on the other hand, is not; it's a sign that you're overdoing it. If you push yourself to work through the pain, you could end up with a very serious injury. So listen to your body. Take a few minutes to rest during your workout if you're hurting, and continue once the pain subsides. Or stop altogether if the pain doesn't go away, and give your body a break from working that part of your body until you feel better.