When David Staley found out that his friend Denis Mikhaylov had broken the Guinness World Record for greatest distance run on a treadmill in 12 hours, he wasn’t impressed.

“I used to run with him in New York,” Staley said. “When I saw that he broke it, I had said to myself , ‘Wow, I think he could have done better.’ I didn’t want to pick on Denis, like ‘Denis, you need to do a better job,’ but I figured why don’t I just go out and do better?”

He did just that on Saturday, breaking Mikahylov’s record of 80.53 miles by running 81.62 miles on a treadmill at the University of Denver’s Ritchie Center from 9:30 a.m. to 9:30 p.m. Staley officially passed the world record shortly after 9:20 p.m. as “Eye of the Tiger” played in the background. He raised one fist in silent celebration but otherwise continued to push forward.

After the conclusion of his 12-hour run, Staley shared a celebratory champagne toast with friends who had come out to watch and cheer him on. The record attempt was livestreamed on YouTube, and as Staley neared the end of his record-breaking run, more than 50 people tuned in to watch.

In some ways, Staley, 30, of Evergreen, isn’t the type of person you’d expect to hold a world record in ultrarunning. Although he’s run in — and won — other ultrarunning events, until February, he ran only “when he felt like it,” which usually amounted to about 30 miles a week. When asked about his preparation, he notes with a laugh that “training is a loose term with me.”

Mikhaylov, who broke the record in New York City in April, said prior to Staley’s attempt that he’s surprised no one has beaten his record yet. He first heard about the record on a podcast and decided to try and break it to show that even though he’s a raw vegan, he’s still a very serious athlete.

The hardest part of breaking the record was the mental challenge of being on the treadmill for 12 hours straight, Mikhaylov added, and he said he’s not sure he’d attempt the feat again. But Mikhaylov said he’s happy Staley decided to try for the record and is continuing to evolve as a runner.

“I’ve run with him before and he’s a very strong runner, both physically and mentally, and I think he has all the qualities to be a Guinness World Record holder,” he said.

But Staley wasn’t even sure the world record attempt would happen until Guinness approved his application two weeks ago — more than two months after he’d originally submitted it. That approval came with about 45 pages of rules Staley had to follow in order for the record to be certified.

Among those rules was that Staley was not allowed to touch the treadmill’s buttons or hold onto its sides during the record attempt. He was allowed to stop to go to the bathroom though, which typically cost him about half a mile each time.

Last week was a whirlwind of last-minute activity as Staley worked to secure a venue and line-up the necessary witnesses (two must be present at all times). He credits his colleagues in The Denver Post advertising department, where he works in digital strategy, with helping him get everything set up in time.

“If I had known how hard it was before then, I wouldn’t have done it,” Staley said with a laugh, a few days before the record attempt.

Though the logistics of planning a world record attempt were all new to him, Staley is hardly a novice runner. His first experience with ultrarunning was when he was 18 and a friend dared him to run from Dallas to Oklahoma.

Staley hadn’t run a mile since high school gym class but he liked the idea of doing something that seemed impossible. He trained for two weeks on an elliptical (he had heard running was bad for one’s knees) and then set off one day in early August running along Interstate 35.

About halfway to Oklahoma, Staley was stopped by a state trooper who said he’d gotten reports of a runaway child. The officer tried to handcuff Staley, so Staley blurted out the first thing he could think of: he told the officer he was running for breast cancer. The officer stopped handcuffing him but proceeded to follow Staley, lights flashing, to the nearest gas station and waited until someone came to pick him up.

Though he never made it to Oklahoma, that dare sparked Staley’s love of ultrarunning. Since then, he’s run and won several ultrarunning events, including the 24-hour Across the Years event in Phoenix and the 24 Hours of Boulder event. He was also the top American finisher in the 125 km (about 78 miles) Canadian Death Race in 2012.

In February, Staley decided to get serious about his running and hired a coach, who got him to start running three times a week. Staley considers himself more of a trail runner though, so training to run 12 hours on a treadmill presented a few challenges.

Unlike trail running, running on a treadmill requires keeping a consistent speed and it also uses different muscle groups. Trail running uses the glutes, hamstrings and quads, but running on the treadmill requires no inner leg muscles at all, Staley said.

“It’s changing the development of my muscles,” he said. “I went on a trail run yesterday and my backside was so darn sore because it’s not used to using those muscles anymore.”

Though Staley runs, he doesn’t like to call himself a runner, because he dislikes all the assumptions that come with that label. What he enjoys most about these timed distance challenges is the ability to compete not against others, but against himself.

“I don’t want people having the wrong impression as if I’m this super-competitive person. I’m not competitive against a field of people. You won’t see me at a 5K stretching,” he said.

“But you know, if it’s some crazy out-of-reach impossible challenge, that’s what I like.”

Jessica Iannetta: 303-954-1510, jiannetta@denverpost.com twitter.com/JessicaIannetta