Regular walks can strengthen connections in and between brain networks, according to new research, adding to growing evidence linking exercise with slowing the onset of Alzheimer's disease.

Published in the Journal for Alzheimer's Disease Reports, the study examined the brains and story recollection abilities of older adults with normal brain function and those diagnosed with mild cognitive impairment, which is a slight decline in mental abilities like memory, reasoning and judgement and a risk factor for Alzheimer's.

"Historically, the brain networks we studied in this research show deterioration over time in people with mild cognitive impairment and Alzheimer's disease," said principal investigator J. Carson Smith, a kinesiology professor at the University of Maryland School of Public Health.

"They become disconnected, and as a result, people lose their ability to think clearly and remember things. We're demonstrating that exercise training strengthens these connections," Smith said.

The study builds upon Smith's previous research, which showed how walking may decrease cerebral blood flow and improve brain function in older adults with mild cognitive impairment.

Thirty-three participants, who ranged between 71 and 85 years old, walked while supervised on a treadmill four days a week for 12 weeks.

Before and after this exercise regimen, researchers asked participants to read a short story and then repeat it out loud with as many details as possible.

Participants also underwent functional magnetic resonance imaging (fMRI) so researchers could measure changes in communication within and between brain networks that control cognitive function.

After 12 weeks of exercise, researchers repeated the tests and saw significant improvements in participants' story recall abilities.

"The brain activity was stronger and more synchronised, demonstrating exercise actually can induce the brain's ability to change and adapt," Smith said.

"These results provide even more hope that exercise may be useful as a way to prevent or help stabilise people with mild cognitive impairment and maybe, over the long term, delay their conversion to Alzheimer's dementia."