Muscle Tensing

Fighter pilots are trained to tense every muscle in their body during high g maneuvers to restict the blood flowing down. This acts like a traffic jam. If the blood can't flow, then it can't leave the brain. This allows the brain to suck up every last bit of oxygen from the blood while it has the chance.

How do fighter pilots not get dizzy?

Fighter pilots have two major tools at their disposal to prevent them from passing out. The first is a tight garment called the G-suit, which squeezes an aviator's legs and abdomen using air pressure, like a blood-pressure cuff.

How many Gs until you pass out?

In 2 G's, we need twice that pressure, in 3 G's, three times, and so on. Most of us would pass out with head-to-toe G forces of just 4 or 5 because our hearts can't summon the necessary pressure. Blood pools in our lower extremities, and our brains fail to get enough oxygen.