1st Lt. Kari Kundert, 8th Operations Group, keeps an eye on time while 1st Lt. Melissa Thurman, 8th Fighter Wing, performs burpees during a CrossFit work out at the fitness center Jan. 23, 2010 at Kunsan Air Base, Republic of Korea. CrossFit combines aerobic workouts with strength training to increase strength, flexibility, agility and endurance. (U.S. Air Force photo/Senior Airman Roy Lynch)