Nature Nurtures.

Researchers at the University of Michigan have found that a 20-minute walk in a park enhances cognitive performance, but walking in a city does not.

The study, reported in the May/June 2009 issue of Psychology Today, explains that unlike urban settings that require intense concentration, greenery, while stimulating, provides gentle concentration, giving our mental muscles a way to refresh.

So if you want to renew your energy, walk among trees.