Australian and international research looked at the data from a long-term health study in the US to check the correlation between vigorous exercise and Alzheimer's-related mortality.
In a new report published today, they state they found that between 20 to 190 minutes of "vigorous physical activity" (VPA) a week could make a difference.
The optimal amount was 140 minutes a week, or 20 minutes a day.
Exercising that much could cut the death rate from Alzheimer's by 31 per cent, the researchers found.
But the catch is that it has to be "vigorous".
No correlation between moderate physical activity (MPA) and a reduced risk of Alzheimer's death was found.
"Vigorous" physical activity was found to be exercise that caused heavy perspiration and large increases in breathing and heart rate.
The researchers also suggested that for older people and people with limited mobility, even short amounts of vigorous exercise could be preferable to longer, lighter activity to avoid illness.
"This study is the first study to investigate the associations between MPA and VPA and Alzheimer's disease-related mortality using a large representative sample of US adults," the researchers said.
