COEUR d'ALENE - Dog-tired, sopping wet and covered in mud, Tom Miller smiled a weary smile.

"Fantastic race," he said. "Cool and rainy - beautiful day for cyclocross."

A bike shop owner from St. Maries, Miller, 41, had just pedaled his single-speed around a sandy, mud-filled course at Riverstone Park. He was one of 108 cyclists, representing various ages and skill levels, who competed Sunday at an Inland Northwest Cyclocross Series event hosted by Vertical Earth of Coeur d'Alene.

And in true cyclocross style, he didn't mind battling the elements.

"This is my season I get to ride, instead of sitting in the store," Miller said. "Really fun. Everything that's good and hard about bike racing in less than an hour."

Soaked by heavy rain, the course was a quagmire - almost 1.5 miles of wet sand, sharp turns and deep, tire-eating ruts (the track was built in a vacant construction area). Riders slogged through mud puddles and skidded across curves. They carried their bikes up a steep, slick hillside. They even dismounted, jumped over obstacles and then mounted again.

The action was fast-paced - each race was only 30-45 minutes.

"It's so intense for a short period of time," said Liz Leston, 43, of Spokane, who would have raced Sunday were it not for a back injury. She was there to support her husband, Shawn, one of the top riders in his class.

"I love the obstacles and the challenge," she said. "It's super fast. It's kind of a neat, different sport. And it's fun. How can it not be fun when you get muddy?"

The event was open to just about anyone, beginner to expert. Ten-year-old Conner Milbrath of Post Falls was the youngest racer, and the over 50 category was full of crafty veterans. Most participants rode cyclocross bikes - essentially a road frame married to fat tires. There was, however, a mountain bikes-only category as well.

"It's a sport for everybody," Leston said.

With five more events on the schedule, the Inland Northwest Cyclocross Series is nearing the midpoint of the fall season. The races began Oct. 3 in Spokane Valley; competitions were held in Spokane and Moscow earlier this month. Upcoming events include races in Walla Walla, Wash., Ephrata, Wash., and Liberty Lake.

The Cyclocross Series finale will be in Coeur d'Alene, at Riverstone on Nov. 21.

Varying conditions make every cyclocross race uniquely challenging, racers said. The Riverstone course, with its tight corners, sand and random patches of gravel, tested everyone's skill.

"It was tough," said Scott Arbuckle, 52, of Spokane. "You hit (the sand) and just kind of come to a dead stop. It was fun, surprisingly."

Arbuckle said he's only raced in two cyclocross events, Sunday's included. A few times his bike bogged down on the course.

"I just had to get off the bike and run through it," he said. "It was like quicksand almost."

Even more experienced racers had some trouble. Still mud-splattered, Mike Mangini, 36, of Coeur d'Alene, a member of the Vertical Earth team, stood next to a warm campfire after the race. He said the wet, cold conditions made for a difficult course.

"It was hard," Mangini said. "It's normally flat and fast, but the rain made it slow and hard."

He likes the exercise cyclocross gives him. All that pedaling, running and hill-climbing add up to a great workout.

"This is just all-out heart rate," Mangini said. "It gets you off the couch on Sundays."