Researchers said they had found a causal link between an increase in strength and better functioning of the brains.
The study saw people aged 55 to 86 with mild cognitive problems carry out a mix of weight lifting and brain training.
The researchers insisted that regular lifting of weight could make one more intelligent especially for people with dementia.
They recommended people should lift more weights so that the world would have a healthy ageing population.
The study was culled as published in The Journal of American Geriatrics Society.