Most people pass out from 5 G-forces. Some of the best fighter pilots can withstand 9. Test pilot Eli Beeding experienced 83 and lived to tell about it.
Before explaining how it's possible, the following is a loose description of G-forces — or G's — on the body, according to Go Flight Med.
Everyone walks around at 1 G, the natural gravitational force of earth. But if you go to space, you experience 0 G's, or weightlessness.
For every G above one that you experience, your weight increases by the G value. For example, if you weigh 150 pounds and experience 2 G's, your weight increases to 300 pounds. At 5 G's, you're weight is 750 pounds (150 X 5).
A person's G-tolerance depends on the body's position, direction, and duration. Someone in the upright sitting position going forward experiencing front-to-back force will pass out at 5 G's in 3 to 4 seconds. On the other hand, someone laying down feet first going forward can sustain 14 G's for up to three minutes.
G-Loc — or passing out from G's — happens when blood leaves the head, starving the brain of oxygen.via GIPHY
Beeding was sitting up going backwards, that is, he experienced the force back-to-front when he came to a screetching halt from 35 mph.
"When I hit the water brake, it felt like Ted Williams had hit me on the back, about lumbar five, with a baseball bat," Beeding said, according to the video description.via GIPHY
Beeding passed out due to shock while explaining his troubles to the flight surgeon. He was rushed to the hospital in critical condition when he woke up ten minutes later.
He made headlines when word got out that he sustain more G's than John Stapp, who previously held the record at 46 G's. Stapp famously used himself as a test subject in his cockpit design research to improve pilot safety against G-forces.
When asked about his achievement, Beeding was quick to point out that he was riding the sled backward and not forward like Stapp. He also said that his time at 83 G's was "infinitesimal" compared to the 1.1 seconds endured by Stapp.
This clip from the U.S. Air Force Film "Pioneers of the Vertical Frontier" (1967) shows actual footage of both test pilots during their tests.