Each step is agonizingly long for Peet who started competing in marathons before her diagnosis, but that isn't stopping her from competing in marathons now.
She's competed in 20 triathlons, marathons and half-marathons since her diagnosis and plans on doing 12 more this year.
"I'm focusing on what I can do, and motivating others to be healthy, and to celebrate what their bodies can do," Peet said.
Peet received an ALS diagnosis three years ago. She's 36 years old and doesn't know how long she has to live.
"You lose the ability to walk, and talk, and speak, and eventually breathe, but right now you have time to do what you love," she said.
While every step might be difficult for her, that doesn't stop her from riding, doing Pilates, swimming twice a week and training for her next half-marathon.
"You just know your life won't be nearly as long as you had expected it to, so in the meantime, you have to make everything count," she said.
"She's been OK with it, and so I'm not going to tell her no," her physical therapist at Duke ALS Clinic, Beth Silberman said.