U.S. Air Force Staff Sgt. Eric Thomsen, 1st Maintenance Squadron lead physical training leader, demonstrates the correct way to execute an exercise during a PT session at Langley Air Force Base, Va., Nov. 22, 2011. Airmen participate twice a week in circuits that are designed to be intense, but informative, teaching them challenging and fun ways to work out to improve their fitness. (U.S. Air Force photo by Airman 1st Class Kayla Newman/Released)