An udarnik (Russian: уда́рник, IPA: [ʊˈdarnʲɪk]; English plural udarniks or udarniki), also known in English as a shock worker or strike worker (collectively known as shock brigades or a shock labour team) was a highly productive worker in the Soviet Union, the Eastern Bloc, and other communist countries. The term derived from the expression "udarny trud" for "superproductive, enthusiastic labour". The ideology behind promoting shock labour was that through socialist emulation the rest of the workforce would learn from the vanguard.