48.6: Percent of Americans who participated in an outdoor activity in 2008. But 43 percent of those participants played outside less than twice a month.

4,857,000: Number of Americans who ran trails last year, up 15 percent from the previous year. Still, trail runners lack the numbers of road runners.

41,130,000 Americans ran on the roads last year. The average runner ran 79 times either on trails or roads.
Source: Outdoor Industry Association

7,592,000: Number of Americans who went mountain biking last year. 38,114,000 people rode skinny tires last year.

22 percent: The increase in participation in telemark skiing and snowshoeing last year, the largest participation increase in any outdoor sport studied.

6 percent: The decrease in youth participation. Of the kids who do still play outside, their favorite outdoor activity is biking. 30 percent of all American youth rode a bike last year.