a set of principles for the efficient performance of vocational tasks. Motion economy was developed largely by U.S. engineer Frank Gilbreth (1868–1924) and his wife, U.S. engineer and psychologist Lillian Moller Gilbreth. Its recommendations include simultaneous use of both hands moving in opposite directions; use of continuous, curved movements rather than straight line motions; use of the fewest movements possible; use of such items as jigs and fixtures to relieve hands of unnecessary work as “holding devices”; arrangement of work to permit an easy, natural rhythm; and arrangement of work to avoid long reaches.