"Rumble, young man, rumble," used to be his battle cry.

But Muhammad Ali is an old man now, ravaged by his years in the ring and his decades of braving Parkinson's disease. The voice that used to bellow that he was "The Greatest" is largely muted now, save for those times in the mornings when he is able to whisper his thoughts.

The face, though, is still that of the most recognizable man on earth. Maybe not as finely chiseled as it was in his prime, but close enough.

"It's not like he doesn't look like himself," said his oldest daughter, Maryum "May May" Ali. "It's the same face, the Parkinson's hasn't affected that.'"

Ali turns 70 today, giving Baby Boomers who grew up with him one more reason to reflect on their own advancing years.

He's fought Parkinson's the way he fought the late Joe Frazier, never giving an inch. But it's a fight he can't win, and nearly 30 years of living with it has taken a heavy toll.

His days at home with wife, Lonnie, in a gated community near Phoenix, generally follow the same routine: He gets out of bed and takes a shower before easing into his favorite chair for long hours at a time.

Sometimes he will watch videos of his old fights. The hands will move, eyes will twitch, as he remembers the magnificent fighter and physical specimen he once was.

"I always say the only person who likes to watch old Muhammad Ali fights more than me is him," said John Ramsey, a Louisville radio and television personality who has been a close friend of Ali's for more than 30 years. "His memory is better than mine and he's very sharp. His sense of humor is still there, too."

Through it all he remains a proud man. There are no complaints. No time spent bemoaning his fate.

It is, the devout Muslim would say, God's will.

"He would always just say to his family, 'These are the cards I was dealt, so don't be sad,'" Maryum Ali said. "He never played the victim. There was never any 'Woe is me.'"

That he is still alive so long after being diagnosed with the degenerative disease may be a tribute to the athleticism and inner strength that helped him stop Frazier on a brutally hot morning in the Philippines and helped him knock out the fearsome George Foreman in Africa. Among the heavyweights of his generation he was a big man, standing 6-foot-2 and usually weighing in at around 210 pounds.

He's stooped now and weighs much less. But his arms are those of a younger man, and his body still shows signs of the magnificent sculpting of days gone by. Every Sunday, his doctor in Phoenix makes a house call to make sure he's doing OK.

There are medications to help relieve his symptoms; there is no cure for Parkinson's.

"The Parkinson's has affected him a lot, one of things he has is a lot of difficulty speaking," said Dr. Abraham Lieberman, director of the Muhammad Ali Parkinson's Center in Phoenix. "But he's never downbeat about it. He's a tremendous inspiration to everyone."

In November, a few days after he traveled to Philadelphia to say goodbye to Frazier, Ali was rushed to a Phoenix-area hospital. His family later brushed it off as nothing more than dehydration.

The fact he was quickly back resting at home didn't surprise those who really know him.

"Ali was always at his best when things were the worst," said Gene Kilroy, his former business manager and good friend. "It's the kind of man he is."

Ali, his daughter says, is in the late stages of Parkinson's now, a time when doctors say patients are particularly susceptible to things that can kill them.

Pneumonia is the leading cause of death among Parkinson's patients, who are also at constant risk for other infections. The increasing inability to swallow can be fatal, and falls are always a major concern.

"He's had a very visible and courageous fight against this disease. He has not given up," said Dr. Blair Ford, a professor of clinical neurology at Columbia University, who specializes in Parkinson's research. "Three decades of Parkinson's is devastating. This is a tougher opponent than anyone he's faced."

How Ali got the disease will never be known, because not much is known about the cause of Parkinson's - other than it is characterized by increasingly severe tremors and periodically stiff or frozen limbs. What is known is that patients gradually lose brain cells that produce dopamine, a chemical key to the circuitry that controls muscle movement, and the treatment is generally dopamine-boosting medication.

Ali once calculated that he took 29,000 punches to the head in a career that spanned more than two decades. He fought without headgear as an amateur, and never backed down while trading punches with brutal sluggers like Frazier, Earnie Shavers and Foreman.

By the final stages of his career, he was slurring his words. Not long afterward, he was diagnosed with Parkinson's.

Lieberman says he doesn't believe Ali got Parkinson's because of repeated blows to the head because he doesn't have classic Dementia Pugilista, which afflicted the late Jerry Quarry, whom Ali defeated twice. Ali is coherent and his thought process is still intact, though the Parkinson's forces him to communicate more with gestures and actions instead of words.

Daughter Maryum believes her father's choice of profession had something to do with his fate.

"In my heart, I think it was a combination of Parkinson's and trauma to the head," she said. "He got hit a lot and he fought for a long time."

Indeed he did. Ali's fights often went 15 rounds and he would often stick his head out and dare opponents to land punches just to respond with some flurries and, on a good night, perhaps even do the Ali shuffle.

The stories of his legendary battles with Frazier and Foreman are etched in the fabric of the times, monuments to a sport that has never been the same since he retired. His fights were so big they had names like the "Thrilla in Manilla" and the "Rumble in the Jungle."

Tim Dahlberg is a national sports columnist for The Associated Press. Write him at tdahlberg@ap.org or at http://twitter.com/timdahlberg