Earlier studies have shown that exercise can increase brain's size and boost the speed and sharpness of thought.
Brains decline as a natural part of the ageing process, which can lead to problems such as difficulty with memory, co-ordination and planning.
Professor Art Kramer, from the US Beckman Institute at the University of Illinois, said that there's a bundle if evidence suggesting that the protective effects of exercise can extend to reversing mental decline.
Research suggests that the benefits of regular workouts are seen not only in those undergoing the normal aging process but also in people suffering from Alzheimer's disease.
Taking regular moderate exercise, just enough to encourage breathlessness, can increase the speed at which our brains think, research has shown.
Research has also shown that exercise can help older brains retain the capacity to grow and develop, known as plasticity.
The latest study has been published in the British Journal of Sports Medicine.
"We can safely argue that an active lifestyle with moderate amounts of aerobic activity will likely improve cognitive and brain function, and reverse the neural decay frequently observed in older adults," the Telegraph quoted Kramer, as saying.
"The effect of aerobic exercise training on cognitive function also seems to extend to older adults with dementia," the expert added.