The Zero-Gravity technology is credited to the scientists and doctors at NASA and was utilized in the space program to reduce the amount of compressional forces exerted on the spine by the extreme speed at which the astronauts blast into space. During take-off, astronauts recline with their feet higher than their hearts with a torso-to-leg angle of 128 degrees +/- 7 degrees, the "Zero-Gravity" position (also referred to as the body’s “neutral” position and the “90/90” position)
The reason Zero Gravity is a preferred posture for astronauts is any slight amount of disc compression will be exemplified by the speed and force of take off. Normal sitting postures can load 150 pounds of compression into the lower back, while standing can load 100 pounds of compression, and lying in a horizontal position can load 25 pounds of compression. Even a minor back or spinal disc problem can be exacerbated with 25 pounds of compression.