U.S. Air Force Staff Sgt. Jason Perkins, 20th Security Forces Squadron (SFS) unit trainer, performs a push-up wearing a weighted uniform during the 20th SFS Combat Challenge at Shaw Air Force Base, S.C., March 24, 2017. The obstacle courses consisted of a 45-pound ruck march, chemical warfare memory games and many other challenges, each focusing on different aspects of a 20th SFS Airman, or defender’s, career. (U.S. Air Force photo by Airman 1st Class Christopher Maldonado)