Jerry Hansen jogs in calf-deep snow, a cold but suitable alternative to sand. (Courtesy Jerry Hansen / January 18, 2013)

Jennie and Jerry Hansen were looking for a 5K to participate in during their weeklong vacation to sunny Newport Beach.

But they didn't know that the race they entered would entail wearing a flak jacket and crawling under a line.

In addition to running or walking on the beach, participants for Saturday's 1st Battalion, 1st Marines Foundation Beach Challenge will also try their hands at some of the training Marines go through, like a low crawl in combat gear, dummy or litter drags, carrying sand bags, a grenade toss and tire flips, according to a news release.

The Hansens, both 51, knowing all that the challenge entailed, donned multiple layers and started practicing in their snowy Afton, Wyo., backyard.

For workout clothes, Jennie wore long johns, a dry-wick, long-sleeve shirt, a fleece jacket, a sweat shirt, a Carhartt coat, a full mask, a neck gaiter, a hood, insulated ski pants and 40-below-zero boots "that go clear up to the knees," she said.

Jerry estimates their boots weigh about 5 pounds each.

Practicing in Newport was more like a vacation.

"When running on the beach, I said, "This feels really easy compared to all the clothes we had on," she said. "A 20-pound backpack isn't nearly as intimidating [after all our other gear]."

So why practice in the snow? Well, it's a good substitute for sand and their backyard is secluded enough to keep people from wondering about their sanity.

If the neighbors saw the Hansens belly-crawling across the snow or running around in snow that went up to their knees, they might think, "Whoa, those people are touched," Jerry said.

Training wasn't all fun and games, though.

"One [event] we were concerned about that we don't want to take too lightly is the litter-carry," he said. "When we think of some of the things Marines have to do, I have to be cautious there and remember what the exercise means."

Jerry's father was in the Army Air Corps, which eventually turned into the Air Force. Jennie believes her grandfather was in the Army, but knows for sure he fought in both world wars.

Jerry anticipates watching the Marines set the standard Saturday, although he doesn't expect to keep up.

"These are young bucks," he said. "We're hoping to move through it and get a medal, get our own dog tags."

Jenny, who is excited but nervous about the event, echoed his sentiments.

"My goal is to finish and not be last in my age group," she said as she laughed.

The 1/1 foundation, as the organization is called, supports a variety of activities for Marines and their families. The challenge's proceeds contribute to that, according to spokesman Bill Long.

The challenge, which is open to all ages and fitness levels, starts at 8 a.m. at Newport Dunes. For more information, visit oneonemarines.com or call (949) 385-1110. Online registration is closed, but spots may be available the day of the event.

jamie.rowe@latimes.com

Twitter: @jamierowe3