Sometimes, running just isn't intense enough for some athletes. They are turning to a much more challenging type of race. They're called mud runs.
More than 500 people turned out for the recent Rock Solid Mud Run at Raceway Park in Englishtown, N.J.
Michael Courtney ran the event with his brother.
"We come out here...good crowd...great people...a lot of fun to help stay in shape...stay active... something to do on a beautiful Saturday afternoon, " Courtney says.
They were there to cover a huge five mile course, filled with huge obstacles and water crossings.... and of course... plenty of mud.
This course is designed by a U.S. Marine, who is still on active duty.
Christopher Roe says, "I've got 22 years in the Marine Corps and my experiences from that is used to design the course. I took some of the stuff from the military and then designed my own obstacles that are original."
They are spread across the 450 acres and seven lakes that make up Raceway Park.
The course features more than 30 obstacles, from a massive multi-part log and metal structure called "The 10 commandments" to a water crossing on a wire.
The fastest contestants can do it all in under an hour. Most take a lot longer.
"Absolutely wonderful. Tough...not easy...but great trails," says Ewa Mobus.
The event attracts people of all sizes and ages, looking for a personal challenge, like Danielle Dalessandra.
"I've been losing weight the last couple of years and I thought it was time to do something different," Dalessandra says.
Most people are able to finish the course with nothing more than some sore muscles and a scrape or two.
A shower awaits to get mud out of every place imaginable.
"Our thing is about giving everything a try. Not everyone can do every obstacle. A lot of people will attempt it. That's what we ask you to do... just attempt it," Roe says.
The event helps raise money for the Semper Fi Fund, which helps injured Marines. The next Rock Solid Mud Run is August 18 at Raceway Park. If you make a donation to the fund, you can get a discount off of the fee. Just use the promo code FOX for a 10% discount.
You can get more information at Facebook.com/rocksolidmudrun.