A Calgary man has just won what might be the toughest multi-terrain foot race in the world.

Charles Miron finished nearly 90 minutes ahead of the second place finisher after traversing lava fields, volcanic steam vents, active volcanoes, deserts of ash, glacial plains, boiling mud fields and jagged rocks in one of the most remote areas of Iceland.

He did it all with a 13-kilogram bag strapped to his back, loaded with sleeping gear, water and enough food to see him through the six-day ordeal.

The Fire and Ice 250-km Ultramarathon spans some of the most rugged terrain in the world, but the harsh physical conditions of –10 C temperatures and sleepless, cold wet nights weren't the worst of it.

"It's 90 per cent mental, and 10 per cent mental," Miron told CBC's The Homestretch.

"Running alone at the front of the pack, there was a lot of time spent in my own little brain," he said.

Nearly 70 competitors from around the world, including two Canadians, competed in the race. Just 40 crossed the finish line. (Bjorn Gunnlaugsson)

By the time he'd crossed the finish line, after 21 hours of exertion, Miron's bruised and beaten body had lost roughly 15 pounds.

"Injury is not something that you avoid in a race like this," he said. "I'm probably gonna lose five toenails."

Racers travelled past scenic landscapes, including waterfalls, grassy valleys and glacial river crossings. (Bjorn Gunnlaugsson)

The race began on the Northern side of the Vatnajokull glacier, almost 100 km from the nearest road, and finished by the coast just below the Arctic Circle.

Of the 69 people to start the race, only 40 finished, Miron said.

Miron spent a full year training for the gruelling race, running an average of 160 km per week in the Rockies to get used to the elevation and jagged terrain during the six months leading up to the event.

"As beings, we tend to put barriers in front of ourselves. If we don't break those barriers, we don't grow," he said.

"This was a way for me to push myself beyond my limits."