Jungle Marathon: Extreme Amazon Race With Heat, Mud and Tarantulas Test Racers' Limits

TAPAJOS RIVER, Brazil Feb. 27, 2012— -- After traveling for 23 hours straight, we tumbled out of a tiny skiff onto a sandbar on an Amazon tributary called the Tapajos River. About 45 minutes later we were awoken by the thuds of dropping mangoes, and some persistent roosters -- all around us, human figures began emerging from the dark jungle -- most of them in spandex.

Some go to Brazil for the beaches, others the cuisine or the nightlife, we came for the pain. Specifically to document the soul-destroying slog called the Jungle Marathon. One of a few ultra marathons in the world this one curled through the jungle for 137 torturous miles over seven days.

And athletes actually pay for the experience of mind-bending agony in this jungle paradise -- the biggest threat the night we landed: giant ants and those falling mangoes.

It was the start of a crazy week-long boondoggle covering what has to be one of the craziest races on earth – the wisdom of which I doubted during several moments of the trip.

We were 200 miles from a Brazilian town you'd never heard of called Santarem, a place where a tableau of human emotions would unfold, where egos would be obliterated and where technology didn't exist.

At the race's starting point was marathon director Shirley Thompson, 55, who has the build of a hummingbird but the mentality of a drill sergeant. She has been organizing this marathon for the past seven years.

Thompson greeted me, "Nightline" producer Eric Johnson and our intrepid cameraman Kenny Chow from her "command ship" -- a jalopy of a ship about the size and shape of a U-Haul.

"Let me see, I will be surprised if, well today I hope everybody will get through, but I would say that probably 65 percent," she said. "We'll have at least a 35 percent drop out this year."

That's her business model. You see if too many people survive this killer race, it'd be too easy and folks don't want to pay for easy. But we would have paid for easy.

We had hauled ourselves to one of the most remote spots on earth to follow a former Miss Florida turned veterinarian named Dr. Juli Goldstein. Goldstein has competed in about 20 marathons, and with her bright pink compression socks, matching pink shirt, and dazzling smile, she looked the part of a beauty queen -- at the start at least. She said was running the Jungle Marathon on behalf of her foundation, Wag-Strong, which she founded after her dog Strider died of cancer last year.

As the only American in the race this year and one of a handful of women competing, Goldstein told me, "I'm still girly, but I have my lip gloss with me just to have something that is a little treasure. You start to appreciate very basic things when you are doing this."

Indeed, the toilets are often holes in the ground or just open forest and everything you would need to survive a week in the jungle -- from antifungal spray to a jungle hammock to food -- is carried on your blistered back -- Goldstein's pack started out at nearly 40 pounds.

PHOTOS: Amazon Jungle Marathon: Where Few Finish

Shocking to those sane of mind, these types of extreme races are booming. In 2006 an estimated 725,000 people took part in such extreme endurance races, in 2010 that number soared to over 1.3 million, an 85 percent spike.

After Shirley Thompson begins the countdown, the race starts slowly with 60 runners slinking into the jungle.

Trying to follow them becomes nearly impossible.

Our guide leads us on a wild four-hour trek through the forest. We ford a stream (bang, my flip camera is soaked and dies) and walk. And walk and walk.

Our cameraman Kenny Chow is bushed. Everyone starts griping. And after we catch up with the racers, we do it all over again, except the tiny skiff that dropped us off has disappeared. We wait like lizards on a pile of rocks – looking out into the river. Hours pass. Finally a villager commandeers a canoe with an outboard engine and we chug into the river at a swimmer's pace.

Now it was me, who wanted to quit -- thinking what a crazy boondoggle we'd gotten into.

After we reach camp, Goldstein straggles in, exhausted. She weeps a little before checking in with the medics.

Every night, the ever-bulging medic's tent would become like a M*A*S*H unit, filled with yelps and grown men screaming. Blisters the size of pancakes were common, toenails peeled off like dry skin -- one runner lost seven by the fourth day.

And rest was fleeting. We were sleeping in hammocks, swinging above the jungle floor littered by tarantulas, and giant ants that left giant scabby welts – and sometimes their heads in, when they bit your feet.

But the distant growl of red howler monkeys and the thunderous snores of cameraman Kenny Chow made the nights tougher. Kenny was incredibly good natured about it, valiantly waiting up until we had all drop off to sleep until he permitted himself to snooze.

"Everybody found it tough today so I'm happy," Thompson summed up after the second day, "That means they got their money's worth! One stage today all the runners were past the checkpoint quite early. I thought, 'Oh this is too easy,' and I was wondering how can we make this difficult tomorrow and I was considering either blindfolding or tying their legs together but we might save that for the third stage."

It was a joke, sort of. Thompson did everything to coax the jungle to do what it does best, rise up almost spitefully against the runners. Coupling the constant companions of heat and permanent dampness to disintegrate all by the most calloused feet and hands.

There were rivers to cross, and storms to weather for the runners. Who kept up the forced march.

By the third day most of the runner's backs had been chafed raw. Many suffered from terrible heat rash and looked like measles victims.

Goldstein was hanging in there, but by the end of the fourth day, she was starting to break down. It had rained most of the day and at one creek, the mud swallowed our cameraman Kenny Chow. Our guides and producer Eric Johnson mostly laughed as Kenny sank, then hauled him out.

We waited for Goldstein for hours by that creek. We heard her sob before we actually saw her. She was being led by another woman -- a hefty British trekker twice her age with Churchillian emotional fortitude.

"Come on Juli, come on, darling," we heard her coax the American, "almost there." They were sliding down a ravine towards us. Goldstein, could barely talk -- she was moaning mostly.

Finally, we all got her back to camp, where she briefly fainted. The medics treated her, and as she rested, a tarantula plopped down from the canopy onto the jungle floor. The runners jumped, some screamed. It was the size of a grown man's hand, as thick and as hairy.

As I was filming it a machete sliced into the frame and chopped the spider in half. I'll never forget how meaty the tarantula seemed inside or that it's two halves kept crawling away from each other. It was then essentially fricasseed by our guides. Runners were told to put their shoes on as other giant venomous creatures took hold of the night.

That night I was certainly thankful for the mosquito net over my hammock -- yes, we slept outdoors every night.

Somehow Goldstein persevered, but the fifth stage was 60 miles long. She ended up getting lost in the jungle that night. The race had disintegrated -- locals had removed trail markers, there wasn't enough water, the runners nearly mutinied and some were simply lost.

We tagged along with Thompson on a 10-hour slog to find them, replace some of the flags and secure water.

Thompson, by the way, was thrilled saying, "This is sorting out the men from the boys today really, there are those that are kind of chill about it, they'll take it in stride and with a lot of them they are getting very irate shouting and screaming and we'll waste excess energy screaming at me rather than putting one foot in front of the other, but you know it's their race."

She estimated fewer than 50 percent would finish. And she was right. Out of the 60 participants that started the race, only 11 finished it in full.

Finally, we located Goldstein, weeping by the side of the road, blowing her security whistle and terrified. But still after a sip of water, she gutted it out and made it to the next checkpoint, but that would be it for her -- and for us.

After a week in the jungle, we flew out. Flying over that jungle and the Tapajos beaches, I couldn't help think to myself: "Maybe I could do this race..." and then thought "maybe not."