At 37, Jennifer Ennis is a bit young for running in the 2008 Umstead 100 Mile Endurance Run this weekend in Umstead Park. The median age of the 250 registered runners is 47, according to Race Director Blake Norwood.

This will be Ennis's first 100-mile race. Her 10-year distance running history includes a 50-mile race in 2006, which she finished in 10 hours, eight minutes.

"After the first 50 miles, the pain is the same for the second 50, so I might as well try for 100," she said.

Chuck Petersen, 67, is a veteran ultra-marathoner. He has completed a dozen 100-mile races, eight of them under 24 hours. He's been training to run the entire 100 miles this weekend, but he's battling a cold, and may settle for just 50.

"I hope to still be running ultra marathons at 70, so I'm not going to push myself," he said.

Ultra marathons are popular. The Umstead race sold out in three days, according to Norwood.

Now in its 14th year the race is one of the best known 100-milers in the country, Norwood said.

"We have people coming here from Sweden, Germany and Canada, plus 35 states," he said.

The fun starts at 6 a.m. April 5 at the Camp Lapiho Headquarters off US 70 in North Raleigh. Runners will have up to 29 hours to finish 100 miles, and the winner likely will come in under 20 hours.

Spectators are encouraged. Visit www.umstead100.org for more information.