One day while Kathrine was running with her coach, who had run the Boston Marathon many times, she decided that she wanted to run it. Her coach Arnie insisted the distance was too long for fragile women to run. Also stating that she would have to prove that she could run the distance before he let her.
After Kathrine ran 31 miles during practice Arnie insisted that she should run the Boston Marathon. Kathrine was planning on running the Boston Marathon unofficially. But, Arnie, her coach, told her it was wrong and she could get in a lot of trouble. As they were registering they checked the rule book which did not have any gender rules. So, Kathrine registered with her initials (K.V. Switzer) since that is how she signs her name. Two weeks before the marathon her boyfriend and the cross-country team coach decided to run with her.
Courtesy of the book Marathon Woman
"Three weeks before the marathon, Arnie and I ran our 26-mile trial. As we came down our home stretch, it felt too easy, so I suggested that we run another five-mile loop just to feel extra confident about Boston."
~ Kathrine Switzer