“For her dissertation, Christensen conducted a field study of 100 milers as they went through the race. She tracked their emotions and their levels of confidence as they journeyed through the various stages. What she found is that runners who were able to accept their pain and not see it as a threat were able to succeed on the trail.

“There’s really something transcendental about that experience,” she says. “People need to go to the edge. Somehow that’s good for us, to be reminded of our mortal limits.

When we push our body to that end it creates such a sense of compassion and gratitude for what your body can do.”