Watch these flight students pass out during high-G training
Someone posted this undated video compilation of airmen going through Air Force G-Force training. From their patches and some of the onscreen text, it looks like they're from Air Force Air Education and Training Command, maybe in the Texas National Guard.
The centrifuge used here is measuring how the airmen withstand rapid acceleration and increased weight. The human body has different levels of tolerance for this kind of acceleration. When the body accelerates, blood is drained away from the brain. Too much too fast will cause loss of color vision, then complete loss of vision and eventually g-induced loss of consciousness or "G-LOC," when the subject blacks out.
NASA has centrifuges to reproduce conditions up to 20gs. The untrained will typically lose consciousness between 4 and 6 Gs. Human centrifuges like these test the reactions and tolerance of pilots and astronauts to acceleration above those experienced in the Earth's gravity. Brooks City Base in San Antonio, Texas maintains one such training and testing center for pilots and weapons systems officers.
This video so much better when the Fatboy Slim music comes up.