Can you give more than 100%?

So, I know the saying is: "Giving 110%"....but can anyone REALLY give more than 100%? We all have the same 24 hours in a day, so does that mean that someone can actually do more than others? And if we give more than 100% where can the line be drawn?

I was watching a tv show this week and someone actually said they were going to give "300%". I mean REALLY?