MCI defines people who have reduced cognitive abilities such as reduced memory, but are still able to live independently. It is a precursor to Alzheimer's disease.

The findings published in the Journal of American Geriatrics show a positive causal link between muscle adaptations to progressive resistance training and the functioning of the brain among those over the age of 55 with MCI.

"What we found in this follow-up study is that the improvement in cognition function was related to their muscle strength gains. The stronger people became, the greater the benefit for their brain," said Yorgi Mavros, researcher at the University of Sydney, Australia.

The study participants were aged between 55 and 86 and were divided into four groups doing either: resistance exercise and computerised cognitive training; resistance exercise and a placebo computerised training (watching nature videos); brain training and a placebo exercise programme (seated stretching/calisthenics); or placebo physical exercise and placebo cognitive training.

Participants doing resistance exercise prescribed weight lifting sessions twice week for six months, working to at least 80 per cent of their peak strength. As they got stronger, the amount of weight they lifted on each machine was increased to maintain the intensity at 80 per cent of their peak strength.

The cognitive training and placebo activities did not have this benefit. The benefits persisted even 12 months after the supervised exercise sessions ended.

"The more we can get people doing resistance training like weight lifting, the more likely we are to have a healthier ageing population," Mavros added.

The study suggested that exercising frequently, at least twice a week and at a high intensity will give the maximum benefit for brain.