After running 125 kilometres over three Rocky Mountain peaks for 12 hours and 47 minutes straight, an Edmonton man took home top honours at one of Alberta's toughest ultra-marathons this weekend.

Alex Petrosky, 34, captured first place at the Canadian Death Race in Grande Cache on Sunday. He cracked the top five fastest finishes in the ultra-marathon's 20-year history.

The gruelling race has left Petrosky with sore legs and blistered feet. It will take weeks to recover, but he said it's worth it.

"The sport — both in community and the lifestyle that it's offered me — has done a lot for me and has become part of who I am," Petrosky told CBC News after the race.

The 125-kilometre trek features a 5,100-metre elevation change and a major river crossing. Racers also had to wade through knee-deep mud and puddles after weeks of rain soaked the trail.

Racers navigate the treacherously muddy trail. (Sean Stephensen/Facebook)

"You're always trying to hop around the major parts of the puddle, but it's inevitable that you're going to be knee-high in some mud," Petrosky said.

"You're just non-stop getting your shoes filled with more and more mud, but it was nice and cool, so you could push on that front."

The race started Saturday morning, with dozens of runners finishing more than 20 hours later.

Petrosky has competed in about 30 ultra-marathons over the past eight years. He ranks the Death Race and the Sinister 7 in Crowsnest Pass as the most difficult.

He said the fourth leg of the ascent — a 1,000-metre climb — in the Death Race is one of the most mentally and physically demanding parts of the trek.

"It's just switchback after switchback after switchback and it feels like it'll never end," he said.

"You almost have to just get into a meditative zone and just say ... 'I'm just going to push and it's going to go away — you're going to get to the end of this.'"

Alex Petrosky at the top of Mt. Hamel along the trail. (Dave Batten)

With the help of nine litres of water and plenty of calorie-rich energy candies, he did just that.

Training weeks included up to 175 kilometres worth of runs, sometimes three per day.

"You're essentially trying to tell your body 'Get ready, you're going to run all the time. You're going to run whenever I tell you to, and you're going to say yes,'" he said.

Race director Brian Gallant said some runners reported this weekend's conditions as the worst they've ever seen.

"Alex's time was incredibly fast considering everything," he said. "Even on a dry, clean course, it would've been a great time. It was a phenomenal performance."

Competitors take on some serious incline in the Rocky Mountains. (Sean Stephensen/Facebook)

He said competitors often wait around after their finish to cheer on other racers.

"Trail runners are such hardy people," he said. "I really love working with them because they have such a great spirit."

Petrosky finished the race around 9 p.m., but stayed at the finish line until 1 a.m., sharing beers with other racers around small pot fires.

"I really like to soak in the vibe of these races," Petrosky said. "There's a really fantastic running scene in Alberta."