Sheilagh admits to being a Ding-Dong-loving, forty-five-year-old mom, 50 pounds overweight, with no significant athletic experience. But she agreed to join the Children's Tumor Foundation Marathon Team, vowing to complete the Portland Marathon on October 1, 2006, while raising funds to help end neurofibromatosis or NF, an often devastating genetic disorder.

Like pregnancy, she had nine months to prepare for the marathon. Nine months to transform from a middle-aged, chubby, sedentary woman to a participant in an activity usually reserved for the elite athlete. The first trimester: an...