Here's an excerpt from the BBC website:
"Walking for 40 minutes a few times a week is enough to preserve memory and keep ageing brains on top form, research shows. Moderate exercise increased the size of the hippocampus, an area of the brain that makes memories, in 120 volunteers. The year-long trial, published in Proceedings of the National Academy of Sciences, showed performance on memory tests also improved."
The article is on this link: http://www.bbc.co.uk/news/health-12325285
Having read the article, here's my suggestion. Play the Proctele game "Elephant Super Memory Challenge: Recall This!" to test your memory. Then take a relaxing walk. Then play the game again. According to the research report you might score better after the walk. Why not have some fun while finding out?