It's hard to say what motivates someone to swim 2 miles, bike over 110 miles and then run a marathon ... all in the SAME DAY.
But some people can do it and do it well.
Here, Kristin is tackling the inaugural Ironman event in Louisville in mid-August 2007.
She set her team's course record on a blistering hot day (at it's peak it was 95 - "cooler" than usual).