The greatest feeling you can get in a gym or the most satisfying feeling you can get in the gym is the pump. Let's say you train your biceps, blood is rushing in to your muscles and that's what we call the pump. Your muscles get a really tight feeling like your skin is going to explode any minute and its really tight and its like someone is blowing air into your muscle and it just blows up and it feels different, it feels fantastic.
Arnold Schwarzenegger