Read this in Men's Health, December, 2008 -
"You may finally have a legitimate reason to hug a tree. A hike in the woods can boost your immunity, say Japanese researchers. They found that men who walked through a forest for a total of 6 hours over 2 days eperienced a 46% spoke in their blood levels of natural killer cells, which are part of your body's SWAT team against invading viruses. Apparently, all trees release airborne chemicals called phytoncides that not only proptest their foliage from microbes, but also help to stimulate our own immunity systems."
There is also scientific studies showing that "forest bathing" (ie, taking a walk in the forest) boosts immune systems through the reduction of stress.
So if you're looking for another excuse to do a long run, just remember it's boosting your immune system! Good stuff.
[photo courtesy of Marc Soller]