Flagstaff, AZ – The run begins at the south rim, dips all the way down to the Colorado River climbs up to the north rim and then back again. It covers 42 miles and ascends roughly 11-thousand feet. Runners must brace themselves for the drastic temperature changes from the rim to the bottom. Nowhere else in the world can you run from the alpine environment to the desert in such a short amount of time.
WOLFE: My very first canyon experience I fell down three or four times. It took me twice as long as it does now so I thought I'd never go back after that first experience.
That's Jason Wolfe who says the canyon's beauty and challenges lured him back to try again.
WOLFE: It was quite a struggle but just finishing it, accomplishing it and turning around and looking at all the ground you just covered feels good. (0:09)
Now Wolfe's training to beat the record time running the San Francisco Peaks in Flagstaff every chance he gets. Last year he finished just 13 minutes over the record, running from the south rim and back in seven hours and 12 minutes.
Up until the 1980s park rangers allowed organized races. But today the national park trails across the country are off limits to official events so athletes track fastest known times on an Internet message board.
Ultra running champion Dave Mackey, who lives in Colorado, is the current record holder.
MACKEY: It's kind of a right of passage in the ultra running world just to do that run. It's something you'll never forget.
TORRENCE: It is the best trail run in the country.
Ian Torrence is a record setting ultra runner and coach based in Flagstaff.
TORRENCE: In terms of difficulty in terms of what you see and experience it blows your mind.
Torrence says ultra running -- that's any race longer than a marathon -- has gotten more popular in recent years.
TORRENCE: Ultra running is a very raw sport it can really rip you down and it just tears away the ego tears away everything that makes you a person Finishing a 100 mile race in the mountains and bringing that experience back to "real life" it's good confidence building. If I can do that I can do anything back here you know.
Some runners have approached the Grand Canyon over confident. Torrence says even strong athletes should take precautions. Marathon runner Margaret Bradley died of dehydration while traversing the canyon in 2004.
TORRENCE: The Grand Canyon South Kaibab trail profile looks nothing like the profile of the Boston marathon and a lot of people forget that. They think I've done a marathon they can do anything that's the thing about the canyon it's a reality check for a lot of people.
A reality check that Jason Wolfe says he's prepared for this time.
WOLFE: I've almost been fixated on it the last 12 months that I really want to break the record now.
Wolfe will attempt to beat Dave Mackey's 6 hours and 59 minute run in early April when he'll take off from the south Kaibab trailhead with nothing but a few water bottles and gel energy packs to keep him going. Wolfe isn't the first to try to beat the record. But he may have the best chance of pulling it off.
In Flagstaff, I'm Laurel Morales.