About 1 million Americans live with Parkinson's disease. While scientists work to find a cure, more and more research is being done around the important role exercise plays in keeping symptoms at bay. Health Reporter Erin Billups has more on one therapy that works particularly well.

Watching Michael Greenberg box, you wouldn't know he has Parkinson's disease.

The retired high school English teacher was diagnosed with the neurodegenerative movement disorder last year.

"It was devastating," Greenberg said. "My handwriting had begun to deteriorate, for one thing. Also, my wife noticed my gait had changed slightly."

To slow the progression of the tremors and stiffness associated with Parkinson's disease, doctors told Greenberg exercising was one of the most important things he could do, which led him to boxing with the Parkinson's Strike Club.

"I feel especially good after I have a boxing session," Greenberg said. "I will be nearly symptom-free, I will spend parts of the day not thinking about being a person with Parkinson's disease, which is a real relief."

A recent study published in the Journal of the American Medical Association found that high-intensity treadmill exercise delays the progression of Parkinson's.

Boxing offers that kind of intense workout and is recommended by neurologists.

"We'll go from jab, jab, hook, hook, to jab, jab, duck," Greenberg said  "So I have to be thinking, I have to be coordinated with my movements."

Launched in 2015, the one-on-one approach of Strike Club is also helpful. It started as one family's attempt to keep their loved one, Donna Leipzig, healthy.

"We heard about doing some boxing, doing some stretching, doing some other exercises, so I got her involved in some classes," said David Leipzig, the founder of Parkinson's Strike Club. "The classes are fine for some people, but not for everybody."

"I felt like I was lost in the crowd," Donna Leipzig said.

Her brother Gary Brill, a lifelong athlete, worked with doctors to tailor training sessions to the needs of Parkinson's patients.

Now, ten years into her diagnosis, Donna Leipzig is still going strong.

"You feel empowered, you feel like you're taking control, you're not just sitting by," she said.

Greenberg also exercises daily, finding strength in being proactive.

"I don't have any illusions about Parkinson's disease: It's a degenerative illness," he said. "One thing that I can do is to exercise."