NEW YORK (AP) -- Freddie Roach's tilted neck and the slight tremor of his hands were obvious to the onlookers at Mendez Gym, as the boxing trainer walked through the ropes and into the center of the ring,

But as the 56-year-old former boxer picked up his pink and blue mitts and started pad work with Chinese Olympian Zou Shiming, Roach's Parkinson's symptoms came to a noticeable halt.

"Again, again, again," Roach instructed Zou, catching every punch the 35-year-old boxer threw his way.

In his 24-hour-a-day fight against Parkinson's, boxing is his comfort zone, Roach says. It was Muhammad Ali's too.

Ali died Friday at age 74 in Arizona following a long battle with Parkinson's -- a disease Roach has been living with since he was 27. The trainer - famous for his work with Manny Pacquiao - has no plans to slow down. He's preparing Zou, who won two Olympic golds and a bronze, for his U.S. debut Saturday night on the undercard of the Roman Martinez-Vasyl Lomachenko fight on HBO.

About 10 to 15 years ago, Roach said Ali and his daughter visited Roach's gym, Wild Card Boxing Club in Los Angeles, completely unannounced. The two men discussed boxing and the medical treatment they were taking to cut down the symptoms of Parkinson's.

"We got to know him pretty well," Roach said, smiling as he recalled the memory. "He played jokes, he did magic, he hit the heavy bag and the best thing for me was when he started hitting the heavy bag, his tremors went away and he had no problems at all and it was like when -- I have Parkinson's also -- and when I get in the ring and get on the mitts with the fighters and so forth, all my symptoms kind of go away so our comfort zone was similar."

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Roach was diagnosed years after Ali was in 1984. At the time of his diagnosis, Ali was 42.

Parkinson's is a chronic and progressive movement disorder of the nervous system. Nearly one million people in the U.S. are living with the disease and presently there is no cure, but there are treatment options to manage its symptoms.

Many doctors believe it can be caused by repeated head trauma, and both Roach and Ali took many punches during their fighting career.

Roach said Parkinson's gets harder to deal with as people with the disease get older. He is younger than the majority of people who have the disease, so he feels like he can deal with it better than most. The Hall of Fame boxing trainer has an alarm system that reminds him four times a day to take his medicine.

When Ali visited Roach, they spoke about their treatment.

"We talked a little bit about the medication at that time," Roach said. "He was having trouble with the dopamine. It's very hard to take. It makes you very sick. It's really hard to get used to and sometimes you rather not take it and deal with the tremors just on your own because the medication doesn't make you feel so well so we hit on that a little bit back then, but that was quite a while ago and the medications are getting better and they're a lot more knowledge about Parkinson's than ever. I think that there will be a cure soon."

When Roach was fighting, his trainer was Eddie Futch, who had also trained Joe Fraizer, one of Ali's biggest rivals.

Back then, Roach didn't think Ali was the best fighter in the world. Now, he does.

"He was a friendly, happy, and just real nice guy," Roach said. "I really got to know him in those four hours."