Scientists examining 124 elderly people found that the oxygen boost resulting from a brisk walk improved mental agility in the parts of the brain that are more likely to waste away during ageing.
Half the volunteers, aged between 60 and 75, did aerobic training and half underwent a course of anaerobic activity, such as stretching and toning, which does not increase breathing rates.
Arthur Kramer, professor of psychology at the University of Illinois, describes in the journal Nature how those people who exercised aerobically performed significantly better at mental tasks controlled by the frontal and prefrontal cortex, the parts of the brain immediately behind the forehead. These areas of the brain govern what psychologists call "executive control" activity, such as planning, scheduling, and short-term memory, which are known to be susceptible to degradation in later life.
"We found that those who received aerobic training showed substantial improvements in performance on tasks requiring executive control compared with anaerobically trained subjects," the scientists say.
Professor Kramer said that during the six-month course the volunteers went from strolling 15 minutes extra per day to walking briskly for up to an hour more than they otherwise would. Aerobic exercise improved reaction time, enabled the volunteers to switch quickly from one mental task to another and boosted their abilities to ignore irrelevant information.
Monitoring of cardiovascular respiration showed just a 5 per cent improvement in the oxygen supply of the lungs was enough to cause the effect. "The improvement we find requires only small increases in aerobic fitness," the researchers say.