Running safety: The road less traveled may have a reason
U.S. Air Force Airmen participate in a physical fitness assessment on the track outside the Aderholt Fitness Center at Hurlburt Field, Fla., July 19, 2011. Knowing which types of surfaces to run on is an important factor to consider when conducting physical training. (U.S. Air Force photo by Airman 1st Class Hayden K. Hyatt)