From the mouth of Dwight Kroening, the first heart transplant recipient to complete an Ironman:
I relate [the Ironman] to what I guess would be like childbirth," Kroening said. "In the process, you're thinking, 'I'll never do this again in my whole life. This is absolutely crazy.' But I think probably about three days later that I started thinking, 'Now this might be something that I might want to do again.'
I maintain this is why they have the athletes who are participating in the races sign up for the following years race BEFORE they race the current year. Ain't no way they'd sign up the next day. And Dwight is also a dude, so he obviously has no idea what he is talking about...we will assume that he has a wife or a woman with whom he shares an illegimate child and she has told him this is how it goes.
In other news, my mom says its okay to think "crotch parasite" is funny AND have children. This is because she A.) really thinks it's okay, B.) is trying to justify why she almost died laughing, or C.) really wants grandbabies and will lie to my face to get them.