In 1944 alone, the United States built more planes than the Japanese did from 1939 to 1945. By the end of the war, more than half of all industrial production in the world would take place in the United States. Wartime production boomed as citizens flocked to meet the demand for labor.
Weight Machines. Machines that work out and build your butt muscles include the leg press machine, smith machine and hip extension. Traditionally, the squat has been the most common exercise for building the muscles in the lower body. The leg press and smith machines assist your body in performing variations of the squat correctly and without injury.
Remove these ads. 1  There are six basic types of simple machines: wheel & axle, pulley, lever, inclined plane, wedge and screw. 2  All simple machines either alter the directions of forces applied to them or multiply their effects.