FOR MORE INFO Thompson's Web site and blog: www.50in50in50.com

Every day, when the pounding on his knees was over, Sam Thompson slid his withering body into a bathtub full of ice cubes.

It kept the swelling down.

Which had helped a lot by Saturday, when the 25-year-old Vicksburg native finished running his 51st marathon in 50 days.

Really. And in four hours and nine minutes.

"To be able to accomplish that is pretty amazing," said fellow runner Leonard Vergunst with the Gulf Coast Running Club in Gulfport.

Thompson, who posts daily summaries on his blog, ran 26.2 miles in Bay St. Louis on Saturday, which followed a 26.2-mile run Friday in New Orleans, which followed a 26.2-mile run Thursday in Dallas and so on.

Between July 1 and Saturday, Thompson ran a marathon in every state, and added one a couple weeks ago in Washington, D.C., just for fun. He ran two marathons that day.

"He's a totally normal guy," said Kirsten Sellereit, Thompson's girlfriend and a registered dietitian who has been with him during his trip.

"He's just very driven. He's got a great deal of passion and intensity."

Thompson says he did it all to raise awareness of the plight of his fellow Mississippians who were hurt by Hurricane Katrina.

Along the way, his story was told in newspapers and on television stations across the country. He is ecstatic about that.

His knees cannot be so happy.

Sellereit said Thompson has had some pain in his knees but is otherwise healthy.

"He hasn't lost a pound," she said, noting that his calorie and fluid intake is closely watched.

She said he went through 11 pairs of shoes during his 1,300-mile journey.

Dr. Steve A. Watts, a sports medicine doctor at the University of Mississippi Medical Center, said he and other doctors are blown away by Thompson's feat.

"It's just awesome," said Watts, the team doctor for the Mississippi Braves and an amateur runner himself. "It's very fascinating to us to watch somebody perform at that kind of level."

He said in addition to swelling, he suspected the ligaments in Thompson's feet and knees suffered and noted Thompson may have to keep an eye on his heart later in life. Such a burst of athleticism might lead to an enlarged heart muscle.

As things went on, though, Thompson appeared to be getting better. Though he had planned all along on taking it easy during his final run in Bay St. Louis, he did not do so in New Orleans on Friday.

He ran his fastest time of all 51 marathons, three hours, 29 minutes, said Chuck George, director of the New Orleans Track Club, which helped Thompson during his day in the Crescent City.

He said Thompson came into the event with some hefty running credibility already; he completed the Mardi Gras marathon in New Orleans last year in under three hours, good enough for eighth place.

"This is just impressive; he's got the strength and the youthfulness to do it without getting injured," said George. "But also, he's really doing it for the love of the sport and to bring help to his hometown."

After the storm last August, Thompson volunteered to coordinate relief efforts at First Presbyterian Church of Bay St. Louis.

He is soliciting donations during his travels for that church and other relief organizations.

Thompson, who was trying to develop a sports clothing line before Katrina, paid for the first half of the trip himself, but picked up a sponsor - outdoors equipment company North Face - several weeks ago, Sellereit said.

Thompson has said he'd always wanted to run a marathon in each of the 50 states and figured doing it all in 50 days would be a good way to drum up some publicity. Especially now, when it seems the national media have all but forgotten that Katrina struck Mississippi before the levies failed next door.

If all this sounds a little too fantastic to be real, consider this: Thompson once ran the entire Appalachian Trail, a 2,100-mile route from Georgia to Maine. Sellereit said he once biked from Canada to Mexico.

Like many others, George said he was skeptical of Thompson at first, but then he looked into his credentials.

"This is a winner here," he said. "He's for real."