"A 2002 study by researchers at Ithaca College compared the moods of college students who ran indoors with those who ran outdoors. The report, published at a conference of the American College of Sports Medicine, found the outdoor runners not only had brighter moods but ran faster than the indoor runners."and
"Trail running is one of the fastest growing outdoor sports...the average runner hits the trails nearly 30 times a year, one of the highest participation rates of any outdoor sport, according to the foundation survey."
Also, links to the "5 best trails in Southern California" and local running clubs. Kudos to Hugo Martin for a great article!