Maybe you’ve hiked from one rim of the Grand Canyon to the other, passing Phantom Ranch and crossing the river at the bottom.

Congratulations, that’s quite an accomplishment.

Now meet Austin endurance athlete Mallory Brooks, 34, who plans to hike from the south rim to the north rim, back to the south rim, again to the north rim and finally to the south rim.

That’s four river crossings. Almost 100 miles. Nearly 4 miles of vertical.

It’s enough to make your quads hurt just thinking about it.

But Brooks, who in 2017 ran the 93-mile Wonderland Trail around Mount Rainier, thinks it’ll be fun.

Brooks and her husband, Jason, own two local trail-running race series — Spectrum Trail Racing, a series of seven off-road scampers, and the Rogue Trail Series, three off-road races in Central Texas. She also coaches the Rogue Trail Project.

She describes herself as “not the fastest runner.” She went to the University of Colorado in Boulder to pursue rock climbing, but she made the switch to trail running in part because it involved less gear. Her first experience was the Pike’s Peak Ascent, which she did without preparing.

“I remember thinking I’ve never run 3 miles, but 13 didn’t sound so bad,” she says. “Then I remember thinking, ‘This would be so fun if I had trained for it.’”

She kept running. Early on, she finished at the back of the pack in 5K races. When she tried a 10K, she finished in the middle of the pack, and a half marathon found her at the front. She ran a 50K and landed in the top three, then won a 50-miler.

“I started to realize that the further I went, the better I did,” she says.

She loves planning and logistics, too, and flips open a notebook filled with graphs and charts and lists of details for her upcoming Grand Canyon run, scheduled for May 2.

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It’ll double the 48-mile rim-to-rim-to-rim hike of the canyon that she and her husband did a decade ago, camping along the way. A few years later, she and two other women ran that same double crossing in 12 and a half hours, and last year she whittled that time to 11 hours and 45 minutes.

But Brooks realized she’d never set a double crossing record, so she decided to double the distance. Her solo, unsupported quad crossing will feature about 22,000 feet of elevation gain. The men’s record for the feat stands at 22 hours and 48 minutes. There is no women’s record yet, because apparently no other woman has attempted it.

“I would like to break 24 hours, but everything would have to go just perfectly and I would have to run it as fast as I did when I did a double crossing,” she says.

She’ll take the Bright Angel trail down from the south side and the North Kaibab to the north side. She plans to start in the evening.

“Ultras usually start in the morning, but my thinking is I’ll go through the dark with a fresher mind and when I’m really fatigued and tired is when the trail will have the most people on it,” she says.

Brooks is targeting a 13.4-minute-per-mile pace on the steep, rugged terrain. She’ll carry all the food she’ll need along the way — chocolate-covered espresso beans, pretzels, dried mango, string cheese rolled inside tortillas and chewy discs made of nuts, figs and walnuts. She’ll also tuck an extra pair of socks, a water filter, a medical kit, an emergency blanket and a map in a lightweight pack, and she'll bring a pair of trekking poles.

Her biggest worry is tripping or falling — and snakes. She won’t listen to music, because she tries to stay hyper-focused and distraction free.

To prepare, she’s running a lot of steep inclines around Austin, including Ladera Norte and the Hill of Life. “I think in a way uphills are easier because there’s no question you’re going to be walking,” she says.

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But fellow Rogue Running coach James Dodds says downhill running is tougher than most runners think, too. “It really tires out the quads, and marathoners who pick downhill races are often surprised by this,” Dodds says.

If Brooks runs too fast downhill, she’ll beat up her quads — which she’ll need for the uphills. Dodds says Brooks’ background as a personal trainer who understands nutrition will help her complete the run. The challenge, he says, will come in running so long and far without a break.

“When you don’t get that day or two down just to let the body replenish and recover but stack on more long mileage, I think that becomes the toughest component,” he says.

Brooks is bracing for some tough mental challenges. “The problem with this run is the halfway point is home,” she says. “You have to decide when you’re there ‘Am I going to go back out and do it again?’”

To deal with that, she’ll compartmentalize it into sections.

“At the beginning you’re a Buddhist monk and super cool and calm,” she says. “You’re watching yourself run with as little effort as possible. Then you transition into a businessman there to do work and hit paces. Then comes the savage — the throw-the-jump-shot, everything-you’ve-got-left person. Whatever you’ve got in the toolbox gets used, and it may be messy.”

And Brooks is fine with messy.