Bucalo, Fagan and Fontana first participated in a Tough Mudder event in April 2011 in Bear Creek, Pa. They all have a running background and figured Tough Mudder would be worth a try.

After finishing in the top five percent of the Bear Creek event, they were invited to the World's Toughest Mudder, the series' culminating event.

They've been hooked ever since.

"At that point, we fell in love with it," Fagan said.

Teammates say they expect to be participating in these events into his 50s, adding that they plan on being "ultra competitive" for the next five years.

Fontana, who has run a number of marathons and ultramarathons, said that being competitive in the events serves as extra motivation.

"Knowing that we can combine the running skills that we have, the strength, the mental endurance, it really balances the playing field," he said.

Although the Tough Mudder series has grown in popularity over the last three years, participants' safety can be a concern.

In April, an Ellicott City man drown while participating in a Tough Mudder event in West Virginia.

While members of 3AM Waterfalls can recount stories of hearing ambulance sirens as they're running in races during the middle of the night, they say they're not concerned about their safety.

"If I know I'm already fatigued, I won't do an obstacle," Bucalo said.

Fontana added that they run the races together and are always there looking out for each other.

"When we were on the course, I can't ever say we were really worried because we've had years of doing this and many months of training," he said.

Bucalo, Fagan, and Fontana knew each other through college and work, but they recruited Lasko through a Tough Mudder Facebook page so they could field a team.

The teammates will look to defend their title at the 2014 World's Toughest Mudder, but in the meantime, they have a handful of training races scheduled in 2014.

They include the 48-hour Spartan Death Race in Vermont in June and the 30-mile Spartan Ultra-Beast event in September.

Fagan said they think they have a strong chance for a repeat. Their training starts Jan. 3 at 3 a.m.

"We're going to be training hard all year long," he said. "We're going to be there and we're going to be the team to beat."

For more information on the 3AM Waterfalls, visit its Facebook page at http://www.facebook.com/3amWaterfalls.