U.S. Air Force Senior Airman Chris Koelndorfer, 1st Maintenance Squadron line delivery and ammo specialist, and Senior Airman Christopher Kelly, 1st MXS maintenance crew chief, flip a tire during a physical training session at Langley Air Force Base, Va., Nov. 22, 2011. The unit’s twice a week PT session gives Airmen unique workout options with inventive activities, including tire flipping, sled pushes and parachute sprints. (U.S. Air Force Photo by Airman 1st Class Racheal Watson/Released)