The Gravity Machine, or Gravity Device, is a device invented by Dr. Brief to help the Z Fighters train under more powerful gravity in order to become stronger and raise their power levels. The machine allows the user to train under Earth's gravity multiplied by a certain number.
The first machine is used to help Goku train in his spaceship for the battle on Planet Namek, and can go anywhere between 1 to 100 times Earth's gravity. The machine goes haywire at one point while Goku is training under 50 times Earth's gravity, causing it to jump up to 100 times Earth's gravity by itself, forcing Goku to master it to the point where he does not even feel it. This remarkable coincidence helps Goku greatly while battling the Ginyu Force. It, along with the ship, are destroyed when Namek explodes.
In the Garlic Jr. Saga, an upgraded version of the machine is created to help train Vegeta. According to the Daizenshuu, this more powerful version can go up to 300 times Earth's gravity. It is destroyed in the Trunks Saga, during training.
During his battle with Pui Pui, Vegeta reveals that he used a third Gravity Machine to train under even higher gravity (in the video game Dragon Ball Z: Buu's Fury, it is said that he trained under exactly 450 times Earth's gravity) and states that Pui Pui is foolish to think that his home planet of Zoon, which had 10 times gravity, could help him win.
Video game appearances
Goku uses the Gravity Machine inside his spaceship to train during his journey to Namek in Dragon Ball Z II: Gekishin Freeza, Dragon Ball Z: Legend of the Super Saiyan, and Dragon Ball Z: Goku Gekitōden. He must train under 20, 50, and 100 times Earth's gravity in Gekishin Freeza and under 10, 20, 30, 40, 50, and 100 times Earth's gravity in Legend of the Super Saiyan.
The Gravity Chamber appears as a training room in Super Dragon Ball Z.