It's never too late to lace up shoes and work up a sweat for brain health as older adults, even couch potatoes, may perform better on certain thinking and memory tests after just six months of aerobic exercise, says a new study.

Researchers found that after six months of exercise, participants improved by 5.7 per cent on tests of executive function, which includes mental flexibility and self-correction.

Verbal fluency, that tests how quickly you can retrieve information, increased by 2.4 per cent. This change in verbal fluency is what one can expect to see in someone five years younger.

"As we all find out eventually, we lose a bit mentally and physically as we age. But even if you start an exercise programme later in life, the benefit to your brain may be immense," said study author Marc J Poulin from University of Calgary in Alberta, Canada.

Aerobic exercise gets blood moving through your body.

"As our study found, it may also get blood moving to your brain, particularly in areas responsible for verbal fluency and executive functions. Our finding may be important, especially for older adults at risk for Alzheimer's and other dementias and brain disease," Poulin said in a study published in Neurology, the medical journal of the American Academy of Neurology.

The study involved 206 adults who prior to starting the six-month exercise intervention worked out no more than four days per week at a moderate intensity for 30 minutes or less, or no more than two days per week a high intensity for 20 minutes or less per day.

They had an average age of 66 and no history of heart or memory problems.

Participants were given thinking and memory tests at the start of the study, as well as an ultrasound to measure blood flow in the brain.

"Our study showed that six months' worth of vigorous exercise may pump blood to regions of the brain that specifically improve your verbal skills as well as memory and mental sharpness," informed Poulin.

"At a time when these results would be expected to be decreasing due to normal aging, to have these types of increases is exciting," the authors wrote.