Maj. Grant Hillman, 16th Weapons Squadron B Flight commander, performs pull-ups at the Warrior Fitness Center on Nellis Air Force Base, Nev., Nov. 10, 2015. A pull-up is a compound exercise which works a large number of muscles in the back, shoulders, and arms at the same time. ( Air Force photo by Senior Airman Mikaley Kline)

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Photo credit: © AB Forces News Collection / Alamy / Afripics
License: Licensed
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Keywords: fitness