The January 24 release of the film Spirit of the Marathon will mark the culmination of four years of film making. But really, the movie is almost 15 years in the making.

The foundation for Spirit—a feature-length documentary about the marathon—was laid back in 1993 when director/producer Jon Dunham was trudging through the Los Angeles Marathon. It was Dunham’s first 26.2-mile race and he didn’t know what exactly to expect. Once he started, though, he wasn’t struck by how difficult it was; instead, he couldn’t believe how easy it seemed.

“I remember when I started it felt incredibly slow and like no big deal at all,” says Dunham. “I could run that pace forever.”

In fact, that pace was even a tad slow for Dunham. So the amateur decided to pick it up, passing other runners to find some space for himself. He knew he was wasting energy by darting around people, but then again, he could run that pace forever, right?

Wrong. Dunham’s zealousness would catch up with him. His legs became heavier. His breaths became harder to gulp down. His strides became a methodical, laborious task.

“I may have gotten up to six or seven miles and started to feel it, and started to see that it was gonna be an interesting experience,” Dunham says. “I do remember when I got to that halfway point, I just got there and I said, ‘Oh my god! I don’t know how I’m gonna make it all the way back down!’”

It took over five hours, but Dunham did make it. And he hasn’t been the same person since. The feeling of empowerment that came with crossing the finish line that day has led Dunham to run over a dozen marathons since. But the run did more than that. Without that (long) tour of L.A., Dunham may not even be making movies.

“It ties into my film career,” Dunham says. “I don’t think it’s any big secret that a career in entertainment and film—that’s a tough path. But it was something that I became interested in, and coincidentally, about the time I ran that first marathon, it sort of awakened something in me that told me that I could do this.”

Now Dunham wants to share that feeling with others—and not just runners. Spirit tracks the stories of six people as they prepare to embark on the Chicago Marathon. Of those six, only two are professional runners. The others include a 65-year-old and a single mother taking her first stab at a marathon.

The film isn’t focused simply on the athletes’ quest to beat a certain time or finish in a certain position. The film is about more than that, what Dunham calls “the transformative experience that all these people have.”

Fifteen years later, Dunham remembers his transformative experience in L.A. Now, with the debut of Spirit of the Marathon, that feeling will be available at theaters nationwide.

Following is a Q&A with Dunham on his film.

Competitor: The website for your film says that this movie will be enjoyed by runners and non-runners alike. What is it about the film that transcends the running world and will captivate people who may never run?

Jon Dunham: This idea of empowerment and personal triumph is really it. It’s something that transcends the sport—and sports in general. It’s something that I believe can be applied to any area of life, not necessarily athletics. When people discover that they have the power, the strength to do stuff that at one point maybe was unimaginable, that’s again just a really incredible experience, and it’s something thematically that the film really drives home and is something people who aren’t runners or athletes will get and be inspired by.

Competitor: The film features six diverse stories, from an expert marathoner to a single mother who is running her first marathon. Why did you think it was important to include all of these unique stories?

JD: From having run the marathon, I knew that there was this huge spectrum of people who ran the race—from world-class athletes to someone who, if you just saw out on the street, you wouldn’t think they’re a marathoner, be it age or physical appearance, whatever. And that was something that was always interesting to me—the cast of characters that were involved. So I wanted to feature a mix of amateur and professional athletes, like the Kenyan runner. I wanted to capture the event through the eyes of someone who had never done it before—what that was like. Those were some of the ideas for the kind of people I wanted to find and feature in the film.

I’m an amateur runner myself. As inspiring as it is to watch somebody like [Olympic Bronze Medalist] Deena Kastor run—it’s always inspiring to see someone so incredibly good at what they do—that’s part of it. But the real heart and soul of the marathon has become the average individual going out and achieving something extraordinary. And that was myself, that was my own story. So that was really ultimately what the film was all about—the transformative experience that all these people have, not just professional athletes.