U.S. Air Force Staff Sgt. Keith Miller, 633rd Force Support Squadron fitness specialist, performs a Total Resistance Exercise suspension training work out during a demonstration at Langley Air Force Base, Va., Shellbank Fitness Center, July 11, 2012. TRX is a type of training that uses bodyweight and gravity to build strength, balance, coordination, flexibility, core and joint stability, all while preventing injuries. (U.S. Air Force photo by Airman 1st Class Kayla Newman/Released)