American boxing legend Mohammed Ali has been on the pro-ring for several years, already afflicted with Parkinson's disease.
This is reported by the ESPN publication on the basis of studies that studied the boxer interview records from 1968 to 1981.
The specialists followed the way in which the champion's speech changed during this period.
Parkinson's disease was diagnosed in Ali three years after his career - in 1984.
However, the first signs of slowing speech, a symptom of the disease, began to appear ten years earlier.
The scientists found out that for 13 years, Ali's speech slowed by 26 percent, and by 1978 had become illegible.
"Ali understood that he was undermining his health, but consciously continued to box," said one of the authors of the study, Jonathan Eyg.
It is interesting that scientists also assure that they discovered a relationship between the slowing down of Ali's speech and the missed blows during battles.