It's well before dawn in Ian Riley's backyard in the Fairmount neighborhood of Philadelphia. He's up so early to train for this weekend's Unite Fitness Decathlon in Wissahickon Creek Park.

He straps on his equipment and gets to work.

"This is a weight vest," Riley explains. "It's got about 25 pounds in here. I don't have a box that's two feet high, so I put this on to try to mimic the height of what's going to happen in the race."

He's talking about box jumps, one of 10 fitness activities that precede a 10K run in the coming decathlon.

There's also a rock hill climb, a lunge walk, and rope pulling.

He'll be competing against his roommate, and as he huffs and puffs and sweats and struggles at this very early hour, it's easy to wonder ... why?

"I think it's just a competitive thing, ya know? In high school, you play sports, then you get out and you've got nothing to do. My buddy brought this up to me and I was like, yeah, that's something I could do. It'd be fun," said Riley.

"At some point, you just do it for fun," agrees Gavin McKay, the president of Unite Fitness and the brains behind the decathlon.

He's seen the popularity of these so-called extreme fitness events skyrocket. Notably the Tough Mudder -- a military-style obstacle course that makes participants swim through pools of icy water, run through burning straw and sprint through a field of live electric wires.

McKay's done the race multiple times. So, being in the fitness business, he made a business decision.

"We wanted to take the next step in where racing is going because it's become so popular and it's gotten really interesting," said McKay. "We decided to reinvent the old Olympic decathlon. So, not just to run farther or bike farther, but actually get fully conditioned."

He has around 100 athletes registered. And he admits they won't have an easy time.

"You might not always feel so good at every moment during a race, or even during a workout, but you know the lift that it gives you," he said. "Most people that are really fit are smiling. A lot. There's a connection there."

The lure of danger

Sports psychologist Joel Fish agrees. Mostly.

"If you look at the theme in all these types of extreme sports, it's that when you've completed something that you never thought you could do, you will feel a deep, deep sense of accomplishment unlike anything else. And that's a very attractive and seductive type of promise to offer people," he said.

After all, what if you can't do it? What if you don't finish? That's a far more likely reality as the events get more and more intense.

"Part of the attraction to this is that there is danger," said Fish. "I get concerned that there are going to be situations that someone can't handle either psychologically or physically, and someone could get really hurt."

Back in Fairmount, Ian Riley's not worried about that. He's just worried about using this race to get ready for the next one.

"In the past I've had trouble with running long distances, like marathons and half marathons," he said. "I think this is kind of like a step up to that. Maybe I'll give that a shot next."

As for his chances in this race? Well, on this early morning, his roommate is still asleep.