Jennifer Lopez, age 39, is in intensive training to compete in her first triathlon in September. She decided she would train for a triathlon while she was pregnant. Now, only seven months after giving birth to twins, she'll be finishing her first triathlon. See her doing the bicycle part of her training in the video below. The very fit woman interviewing her is chief editor at Self magazine, and she is also training for the same triathlon, but in her case it's not her first one, it sounds like she's already got a few behind her.