(CNN) For years, Dan Schoenthal had in the back of his mind that he wanted to hike the Appalachian Trail. That goal took on a new sense of urgency after he was diagnosed with Parkinson's disease in 2015.
He hiked part of the 2,200-mile trail last year, just to see whether he could do it -- and now, six years after his diagnosis, Schoenthal is aiming to hike the rest.
Parkinson's disease is a neurodegenerative disorder that affects nearly one million Americans, according to the Parkinson's Foundation. It's the second most common neurodegenerative disorder, behind only Alzheimer's disease. Parkinson's patients typically experience a tremor, slowness of movement, stiffness, or gait and balance problems. But many can still live a full life.
"A diagnosis of Parkinson's disease is not a death sentence," Dr. James Beck, senior vice president and chief scientific officer of Parkinson's Foundation, told CNN. "It is a disease people struggle with over time, but it is one that people can still live their lives with."
There is no cure for Parkinson's, but there are medications to help patients deal with symptoms. Exercise is also recommended to help patients maximize their quality of life.
Schoenthal, 56, told CNN that when he was diagnosed, his neurologist stressed to him that exercising was just as important as, if not more important than, his medication. All the more reason, he says, to get on the trail now.
The Appalachian Trail is the "longest hiking-only footpath in the world," according to the Appalachian Trail Conservancy. It passes through 14 states from Georgia to Maine.
Of the thousands each year who attempt to hike the whole trail -- what's called a thru-hike -- only one in four makes it all the way, the Conservancy says.
Schoenthal, of Great Valley, New York, did the first 300 miles of his journey last August, with a plan to hike just in August and September to see whether he would be able to take on the feat. He started back up April 3, with the goal to finish the remaining roughly 1,900 miles by the end of July or early August.
He spoke to CNN from mile marker 413, near the Tennessee-North Carolina border.
"I wake up a little stiff and sore every morning, but I stretch out and get my gear together and by the time I eat a little breakfast and have some water, I'm usually pretty good to go," Schoenthal said.
He's taking on this challenge not just to reach the goal he's thought about for years or to keep his body moving. He's also raising awareness of the disease and funds for the Parkinson's Foundation, a non-profit dedicated to improving care for those with Parkinson's and finding a cure.
"We don't know for the vast majority of people what causes their Parkinson's disease, how Parkinson's progresses or how to stop the disease itself," Beck told CNN.
Another difficulty with the disease is diagnosing it.
"It's not a disease you can diagnose with a blood test or brain scan," Beck said. "It's often a diagnosis of exclusion," meaning doctors often eliminate other causes of symptoms first. With most not getting diagnosed until at least their 60s, Beck said it can be a particularly frustrating for younger patients to be diagnosed.
"Clinicians are not expecting Parkinson's disease in someone in their late 40s, maybe early 50s, so getting an accurate diagnosis can take a little while."
Schoenthal said it took almost three years for him to get his diagnosis. He said knew something was off while he was training for a marathon in 2012, after completing a half marathon.
"I started having shortness of breath and my legs started dragging. I was doing a 3- or 4-miler and I came home and told my wife, 'Something just ain't right. I don't know what it is, but something ain't right.'"
He was diagnosed with an essential tremor, which Beck said is a common misdiagnosis Parkinson's patients receive.
Over the next few years, Schoenthal said, his muscles got stiffer and tremors got worse. In 2015, he got the Parkinson's diagnosis.
Schoenthal said while he has a tremor in his left arm and left leg, he hasn't seen much progression of the disease, which is why he knew this was the year to take on the trail.
"I'm going to listen to my body and if my body says to slow down or stop, that's what I'll do. But so far, so good."