The idea for GPK germinated in the 1980's when Kurt Simonson, a tetraplegic (quadriplegic) due to a C4-C6 spinal cord injury, couldn't find any equipment that allowed completely unassisted upper-body and aerobic rehabilitation, as well as conditioning, to improve and maintain functional independence.This led to the UPPERTONE and GPK's formation. And even though prototype model of the UPPERTONE was first displayed at the 1990 Los Angeles Abilities Expo, the UPPERTONE is still the only machine on the market that allows people with quadriplegia due to spinal cord injury or other causes to exercise and rehabilitate themselves truly independently. It does not require wrist cuffs. Its unique design and features allow quads to move around and between its three stations, as well as vary resistance, without assistance.