MIAMI Personal trainer Craig Marks wants to help his clients slam Parkinson's disease with a knockout blow - literally.

Marks and his fellow trainer Onyedikachi Ibeji, who run a gym in Davie, Fla., lead a group of about eight Parkinson's patients twice a week through a workout routine that includes boxing. And they swear by his unconventional methods.

"I hadn't climbed steps in 10 years" before starting to work out with Marks and Ibeji, said Robin Caradonna, 61. She's had Parkinson's for 15 years, but barely used the railing while scaling two flights.

There are 1.5 million Americans living with the disease, according to the National Parkinson Foundation. The illness is a degenerative condition where the brain doesn't produce enough of a chemical called dopamine.

That chemical is needed to transmit signals to muscles. People who have Parkinson's can't control their muscles well and, over time, they develop endless tremors or lock up into rigid positions.

Boxing, along with other exercises like jogging, crunches and medicine-ball tosses, helps fight those symptoms and keep muscles strong, Marks said. Even though his Parkinson's clients hit punching bags and not each other, Marks and Ibeji do not go easy on them.

"This promises to be very, very painful today," he told Abe Taback, 63, on his third visit to the class.

"I tell you, he's a killer," said Taback, laughing. Marks laughed too - but he hadn't been exaggerating.

Taback sweated as Marks pushed him to do crunches. He grunted while swinging at Marks' gloved hands - left jab, right, left, with a quick counter-feint from Marks to keep him on his toes. Pretty soon Taback, who's had Parkinson's for 15 years and shakes regularly, was even jumping up and down for the first time in years.

"I haven't done this before!" Taback panted.

"Well, you're doing it now," said Marks.

Then it was back to the punching.

"It's far from easy. It felt like I went through a 10-round fight with (Muhammad) Ali and I wasn't the winner, but it's worth it in the end," a tomato-red Taback said after an hour.

For Marks, his job is personal. The 42-year-old Miami native spent plenty of time with physical therapists and personal trainers following a bad neck injury when he was a wrestler at the University of Tennessee. Then, Marks' father was diagnosed with Parkinson's more than a decade ago.

When Marks saw that normal physical therapy wasn't helping him, he designed his own program.

Although his father passed away three years ago, Marks said he saw him improve thanks to the workouts. He decided to offer his training program to others.

Malka Silk, 77, of Tamarac, Fla., has been working out with Marks for several months. "I've worked with many physical therapists, and these guys are different," she said. "They have heart."

"And I have this nice young man to help me with my punching," she said, smiling at Jake Marks, Craig Marks' 12-year-old son, who helps out at the gym during the summer.

Getting out aggression is another key benefit. With a pair of boxing gloves strapped on, the 98-pound Silk whaled away on a punching bag like Ali in his prime. In 1983, Ali was diagnosed with Parkinsonism, a movement-disorder syndrome that mirrors Parkinson's disease.

"I get very angry that I even have this lousy disease," Silk said.

Similar programs using nontraditional exercises have shown encouraging results. A study published last year by researchers at the Washington University School of Medicine in St. Louis showed that Parkinson's patients who were taught the tango in place of standard exercises gained more balance and could stand up from a chair and walk around more easily.

Only about 10 percent of Marks' clients are disabled, he said. The rest just want a personal trainer.

The Parkinson's class costs $15 per session and Marks said he donates profits to a Parkinson's charity.

Next month, Marks said he is meeting with a neurologist from the Cleveland Clinic in Weston, Fla., who is interested in studying his methods.

Marks views his program as a personal mission. "As long as I have the strength, I'll keep doing this," he said.

To find out more, contact Craig Marks at 954-707-9175 or go online to http://first-fitnesstraining.com.