High-G training is done by aviators and astronauts who are subject to high levels of acceleration (G). It is designed to prevent a g-induced Loss Of Consciousness, a situation when g-forces move the blood away from the brain to the extent that consciousness is lost. Incidents of acceleration-induced loss of consciousness have caused fatal accidents in aircraft capable of sustaining high-g for considerable periods. This is a classic example of g-force training. You get to see these pilots' faces as they experience tremendous amount of pressure under these g-forces. Funny stuff!