The Universal Sports article explains why this was voted best dramatic moment of 2009 with lots of flourish and details:
"...You can always tell how the race went and how happy I am just after a race just because of my reaction after it," Phelps told Universal Sports recently. "I went absolutely crazy after that race. I've never celebrated like that before. I took six months off, and being able to be the first person to break 50 [seconds], there was a lot of emotion in that race."
I love this reaction from Phelps too.