U.S. Soldiers assigned to 1st Battalion, 3d Brigade, 9th Cavalry Regiment, perform burpee exercises while wearing protective masks on Contingency Operating Base Delta in Wasit province Iraq, July 15, 2011. A burpee is a full body exercise used in strength training and as aerobic exercise. This is one of eight events taking place during a competition conducted by Soldiers of 9th Cavalry Regiment in celebration of their 145th Birthday.