It's daunting, daring, and downright dirty. However, getting to this finish line is grueling.
"Crawling through mud is just fun," said April Boyd.
"People love a challenge," offered trainer EJ Diaz.
Taking up the challenge are a growing number of women.
"The first year I was scared to death," Boyd continued.
Boyd, 31, is one of the ladies looking to push her body beyond its limits.
"I've done a half marathon, which is about the same distance, and I was bored to tears," she said.
There's nothing boring about this workout.
"'Tough Mudder' has built itself as the toughest workout on the planet," Diaz explained.
Designed by British special forces, Tough Mudder is hard, but Sparta trainer Diaz works his students even harder.
"People will say that our training program and the training we have is a lot harder than the actual event itself," he said. "We flip tires, we swing sledge hammers, we climb walls."
"I knew if I could do this, I could do probably, just about anything," Boyd said.
For some, it's also a chance to overcome fears.
"I'm scared of heights," explained Ruth Slagle, 51.
So just days before the Tough Mudder, she confronted her fears.
Each time she does it, it gets easier, but her fear isn't completely gone.
While Ruth confronted heights, April took a fall, but she knew it's all part of getting ready for the big day. It's the day the runners come face to face with other Tough Mudders to do everything it takes to cross the finish line.
"Like jumping into an ice bath, jumping off of a 15-foot ledge into water or crawling through really confined spaces," she explained.
Helping each other climb through each stage, they're running on adrenaline and getting dirty, but loving every minute of it.
"Running through the last obstacle is electroshock therapy, so you're running through live electrical wires after they hose you down with water," Boyd continued.
Yeah, it sounds and even looks like torture, but what was once a masculine military idea is growing on women who look at miles of mud, saying, "Bring it on!"
"It's just a sense of fulfillment and accomplishment and pride," Boyd added.