5:00 a.m. Sunday morning found me in running clothes outside my house, alone in the dark. I was, however, warmed up and ready to head off on a race with over 120,000 others around the globe. A app on my phone counted down to zero, and I was off. Unlike other races, however, I didn’t know exactly how far I was going.

I was participating virtually in the 6th annual Wings For Life World Run, a unique event where, instead of seeing how fast you can go over a set distance, runners see how far they can go before being overtaken by a “Catcher Car.” Starting 30 minutes after the runners set off, the Catcher Car first cruises at a 6:51 min/mile pace for 30 minutes, then it speeds up to a 6:26 pace for 30 minutes, and so on, until, 4.5 hours into the event (if anyone makes it that far), it is zipping along at 21 mph or 3 min/mile.

In 12 locations worldwide—ranging from Melbourne to Munich, Pretoria to Poznan, Poland—there is an actual car on the route, complete with sirens and music to warn runners it is approaching and a chip reader that captures info from the runners’ tags as it rolls past. At more than 300 other gatherings world wide, and untold individual runs like mine, the car is virtual, a predator stalking us on an app.

Whether real or virtual, when the car catches you, your race is over.

Wings for Life World Run in Pretoria, South Africa
Wings for Life World Run in Pretoria, South Africa // Sam Clark for Wings for Life World Run

The dynamics of the race are intriguing, and more than a little confusing. As I headed out, I realized that, unlike any other race, the faster I go the longer I’ll run. It’s unsettling to me, I can’t quite get my mind around it. As the central governor theory explains, much of our sensation of fatigue and the ability to pace ourselves is based on an internal assessment of how far we have left to go. What happens when that mark, the finish line, is the variable?

“That’s really what excites me most about the race, is that you don’t know how far you can go,” says Dan Berteletti, an ultra runner who won the 2017 US race in California by going 43 miles in “about 4 and half hours” before the car caught him.

The race does, fortunately, provide a handy goal calculator to get some idea of how far you’ll make it at different speeds. It shows, for example, that if you want to cover 10K, you’ll need to run 11:35 min/mile and you’ll be caught at 1:12 into the race. To stay ahead of the car for a half marathon, you need to be running 8:27 pace and will be on the course for 1:54. Berteletti, an engineer, says, after some calculations, he told himself, “I think I can run about 6:30 per mile pace. That would get me to 41, 42 miles—and that is further than anyone has gone in that location.”

Dan Berteletti
Winner Dan Berteletti of United States during the Wings for Life World Run in Santa Clarita, California, United States on May 7, 2017. // Chris Tedesco for Wings for Life World Run

He did just that, pacing himself steadily until he had passed everyone else sometime between mile 38 and 39. “I had only planned to run 41 miles,” he recalls. “So once I was in the lead, I thought, ‘What do I do now? I’ve had enough, I’m good.’” He kept going, but slowed once he knew he would win, and let the chaser car catch him after 43 miles.

Last year, Berteletti ran in Croatia, a huge event with 10,000-plus participants (the event is much bigger globally than in the U.S.), and found himself in seventh when he heard the car approaching. “You know it is close, so you put in that final burst,” he says. He went after a runner about 200 yard ahead of him. “I didn’t catch him,” Berteletti recalls, “But I felt like I put in a good effort before boarding the shuttle bus back to the start.”

This final surge provides much of the drama for runners, most of whom end up completing somewhere between a 5K and half marathon. Even if you’ve slowed or are walking when you hear the car approaching, you find a reserve, Bertelleti says. “You do a mile, half mile, do something you didn’t think you could do—and maybe that changes your perspective the next time you run.”

Wings for Life World Run in Vienna, Austria
Wings for Life World Run in Vienna, Austria // Philipp Greindl for Wings for Life World Run

The idea of a pursuer bearing down, even long before you see or hear it, provides motivation throughout the run. The fear of being chased (and eaten) is buried deep in our psyche. In a poll conducted by the Wings for Life organizers, a majority of those who went farther than expected exceeded their goal by an astonishing 5 to 15km.

As for me, running alone on dirt roads of the high plains with my three dogs, I lacked some of the motivating excitement. I had planned to run a half marathon in negative-split fashion, so I started easy and warmed up as the sun rose. After 30 minutes, the app told me that the car was underway, and just knowing it had started to close the gap caused my splits to drop noticeably. But the car was far enough behind and approaching slowly enough that I still thought I could treat it like an easy run and not have my goal threatened.

I turned around after 7 miles and sped up a bit, but not much, wanting the chase to feel real as I approached the half marathon. At nine miles, the app said the car was still over a mile behind me and I was rolling along, confident I could stay ahead and looking forward to speeding up as it got close.

But then, around the 10 mile mark, my dogs got in a fight with a raccoon (you can’t make this stuff up), and it took a couple of minutes until we were solidly on the way again. A half mile later, the app suddenly said, “The catcher car is approaching.”

When I pulled my phone out to look, I found the car was 900 feet behind and closing fast. I took off like a scared rabbit—or maybe a raccoon—chased by a pack of dogs, and managed to get in three quarters of a mile before the app told me I had been caught at 11.48 miles.

Wings for Life World Run in Kakheti, Georgia
Wings for Life World Run in Kakheti, Georgia. // Tamuna Kulumbegashvili / Red Bull Content Pool

After the initial dejection, I settled in and finished the run, passing the half marathon only a couple of minutes behind my goal. But a few minutes were all the catcher car had needed, as it was flying along at sub-6 pace by then. I realized my calculations had been off and my negative-split strategy flawed, compounded with that bit of bad luck. Even though I hadn’t treated it as a race, I was disappointed to miss my goal—which made me eager to try it again and take it more seriously. I was bitten.

And that’s the lure of the Wings for Life World Run format: A new, compelling running challenge to try to master. Berteletti, running this year’s US race on a hot and humid day in Florida, pointed out another aspect of the format that plays with your mind. “I struggled with the fact that I could dictate my finish line,” he said, “And I was OK with the end of my race coming sooner than I had envisioned in my preparation.”

In the end, he managed 23.7 miles this year. Granted, the chaser car’s pace has been adjusted to go faster in later stages than it had in the past, but he admitted that the heat and humidity, combined with less-than-ideal fitness after recovery from an injury, affected with his motivation. “I didn’t quite have the killer instinct out there, and instead was just happy to be running healthy, and allow my body to live and run another day.” That’s another unique aspect of the format: Whatever you can give on the day is enough. Everyone finishes.

When you’re at an actual race, you then get to board a shuttle bus back to the start. That’s another one of Berteletti’s favorite parts. “Besides the air conditioning, it’s a pleasure to sit in relief with the other competitors and chat about how the day unfolded,” he says.

Global winner Ivan Motorin
Global winner Ivan Motorin of Russia, Wings for Life World Run in Izmir, Turkey // Nuri Yilmazer for Wings for Life World Run

The top performances of the day were set in much cooler European venues: Nina Zarina of Russia, running in Zug, Switzerland, covered 33.37 miles. On the men’s side it was fellow Russian, Ivan Motorin, who ran a world-best 39.95 miles in Izmir, Turkey. Beyond the joy and excitement the running brought, the event raised nearly 4 million dollars, all of which goes toward spinal cord injury research.

Next year’s global run will occur on May 3, 2020. I’m planning to try it again, next time more seriously; I’d like to set a mark I’m proud of. And maybe I’ll join a group where I can get the full run-’til-you-get-caught experience. I’d like to fully experience what Berteletti and his wife, Julia, say is, “The funnest race we’ve ever run—that nobody has heard about.”