His fellow motorcycle racers don't know what to make of Roger Hurd.

"The guys see me hobbling around the start line. Then they drop the flag and it all goes away," Hurd said.

Hurd has a handicapped placard hanging from his rearview mirror and when he heads to the starting line at races, his gait is slow and unsteady. He suffers from Parkinson's disease, a degenerative nerve disorder that causes muscle tremors, joint stiffness, slowness of movement and affects victims' balance.

"Everybody's been open arms. Everybody's been great," he said. "My biggest trouble is walking; if I have to walk long distances, it kills me."

Hurd doesn't seem capable of riding in a grueling off-road motorcycle race, much less winning them but that's exactly what he's doing.

"When I ride, I don't shake. I actually feel normal. So I try to ride as much as I can," he laughed. Doctors tell him that the riding actually works all of his muscle groups, and is therapeutic. "Everything just seems to go away."

Hurd had the symptoms of Parkinson's disease for years, but it wasn't until 2008 that he actually discovered the tremors and reduced endurance were anything other than pinched nerves or exhaustion. A former professional racer, he ranked second in 1991 and 1992, 125-cc class motorcycle-racing category in the American Motorcyclist Association's District 37.

After being diagnosed with the disease, he rode in the grueling Baja 1000 for the first time in 14 years in 2009, and again in 2010.

"Last year, I probably did eight or 10 races," he said.

And he isn't slowing down: Hurd has picked up additional sponsors and will probably race in 14 to 15 races this season.

"I've been getting better and better as I get stronger," he said. He's had three wins in the over-40 senior division this year, including two over Mother's Day weekend. In his prime, he was ranked second place in the district, two years in a row. (The AMA ranking is based on points accumulated in the top 20 finishes a rider had in a given season, although only a fraction of all competitors race 20 or more times. Hurd hasn't done so since 1992.)

"I've had to change up my riding style a bit, because it takes a long time for my muscles to move," he said.

As the messages take longer to go from his brain to his hands and feet, Hurd has to think about his turns further in advance, and he's modified his motorcycle to account for the progression of his Parkinson's.

"I'm feeling really comfortable on the bike and it shows, because I'm getting better and better." Hurd's doctors are on board with his racing-as-physical-therapy regimen. "They tell me to do it as long as I can, as long as I feel comfortable."

Still, there's no question that Parkinson's will ultimately pull out ahead of Hurd.

"At this point, we're in a pretty good race," he said. "I know I've only got a couple of years left that I can do this as a top runner. ... But I'll ride as long as I can."