Staff Sgt. Adriana Bitker, 341st Medical Operations Support Squadron physical therapy technician, demonstrates a plank during a core stability class while Senior Airman Kaitlyn Callahan, 341st MDOSS physical therapy technician, monitors the timed exercise Aug. 2, 2017, at Malmstrom Air Force Base, Mont. The core stability class focuses on core muscles to aid in the prevention and strengthening of commonly injured lower back muscles. (U.S. Air Force photo/Staff Sgt. Delia Martinez)