I was given these warnings: You're going to be filthy. Your clothes and sneakers are going to weigh you down.
You will feel it in your forearms, fingers and all of your leg muscles.
I'm not a freakish athlete like Usain Bolt, but I'm in good shape. Really, how hard could running through mud be?
Oh, I had no idea.
On Sunday, a friend, Katie Toole, and I went to the McGrady Training Center off Leesburg road to test the course for Saturday's USMC Ultimate Challenge Mud Run.
The 1,800 teams - a total of 7,200 people - should prepare well in advance. This isn't a light jog so don't bring your iPod like some runners in the past. This is a test of endurance, strength and will.
Maj. Jim Williamson, a U.S. Marine whose team has dominated the mud run the past two years, took us and a photographer on what began as a leisurely stroll through the wooded course.
Then we circled around a ridge where we were met by an obstacle new to the course this year - what Williamson called "a big, deep water hole."
To get into the 14-feet deep hole, we had to jump down 12 feet. Katie and I thought about that for a moment, but if you're running the course, any hesitation will cost you time.
We jumped. Katie held her nose. I kind of grunted - I won't say it was a yell or scream - and I swallowed a few ounces of dirty brown water.
"You guys were up there a long time," Williamson would later tell us. "I didn't know it was that high."
We swam the length of a pool to the shore, pushing through muck on the water's surface that reminded me of the top of a root beer float.
Then we climbed a short hill, my water-logged and mud-caked shoes making me look like Herman Munster walking up steps.
How can anyone run like this?
"I run as fast as I can through the entire thing," Williamson said. "I don't stop until I get done. It's a long and demanding course."
We walked to the next obstacle, hands on hips.
Our clothes clung to our bodies, adding extra weight. Bugs nipped at us. Water sloshed in my sneakers.
The mud run is in its 16th year. This year the course is 4.2 miles long, and there are 30 obstacles to, as the Marines say, negotiate.
Some, like the rope swing, take little effort.
Others, like crawling under Light Armored Vehicles while going through a 3-foot-wide trench, demand patience.
Williamson is the perfect course motivator, the Bear Grylls of the mud run, if you will. Last year his team set a course record, finishing in 36:25.
He doesn't duct tape his shoes for better traction. He doesn't wear gloves for better grip. He doesn't even wear a shirt. The running shoes he wears are perforated for drainage, and he begins breaking them in the day after the past year's race.
But back to the course. It's difficult to set a steady pace. There's a lot of elevation and misdirection, and if there's a bottleneck at the obstacle, you have to wait.
If there's a competitive team trying to climb over you, you treat the race like golf and let them play through.
And don't forget the mud. If you're on a team running after midday, mud is all you'll see.
"Anything you bring on this course will be thoroughly destroyed," Williamson said.
There are only two obstacles that require all four members of a team. One is the stretcher carry, where three members have to run the fourth, on the stretcher, across the finish line.
The other is a 10-foot vertical wall. Williamson has his technique down. Clasping his hands together, palms up, he put them on his knee. I placed a muddy shoe in his hands and pogoed to the top of the wall, trying to catch a groove in the wood.
I was able to kick a leg - "chicken wing your leg," Williamson said - and roll onto the top. Next, Williamson did the same for Katie. Lying on my stomach, I had to grab her and help lift her over.
But how does the last member get over the wall?
Williamson, with his arms raised, jumped vertically, and Katie and I tried to grab his wrists.
Sounds simple, but it took at least four tries to catch his wrists (our hands were still wet), and then we strained to help him walk up the wall. I asked how many seconds we would've cost him in the race.
"A few," he said, his competitive tint apparent.
I felt I had done enough reporting, but the Z Trench awaited. First, we sprinted up and down six high mounds of dirt and then dove into the water.
The Z-shaped trench has varying depths. I was walking in knee-deep water when I turned my head to check on Katie. On my next step, I plunged under water.
This happened several more times. At one point, I took a seat and enjoyed the cool water, like wading in a kiddie pool. I thought about a shower.
Like a lot of competitors, Williamson tosses his shoes into one of the dumpsters at the finish line. I let my shoes go, too.
After the run, I uploaded a photo of my departed sneakers to my Twitter account. A friend, who is running the course for the first time, sent me a text: "How was the mud run? Tough?"
My response: "You have no idea."