On Sunday, more than 50,000 athletes are expected to compete in the New York City Marathon, one of the largest, and most elite marathons in the world. Running a continuous 26.2 miles is a major physical challenge. But what exactly is happening in the body when running such a long distance?Joining guest host Rachel Feltman to answer questions from long-distance runners is Dr. Brandee Waite, Director of UC Davis Health Sports Medicine. Over the past 20 years, Dr. Waite has directed the medical care for multiple marathons and ultra-marathons, and has served as a team physician for USA Track & Field.Transcript for this segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.