Official Entry: "GravBall is a fast paced aerial version of Soccer where the players use anti-grav backpacks to fly around an immense stadium. Due to the fast and violent nature of the game, players wear tough armor, injuries are still common though. Cybernetic implants are used to substitute for mangled limbs, but a GravBall player must be at least 50% original human flesh in order to qualify in the GravBall league. Due to the popularity of the sport the GravBall League, which owns all the stadiums in the city, has become a prosperous corporation. However, alternative recreations such as Sensovision or the illegal Psiclone are proving to be serious competition."
The Gravball League does not provide any services to X-COM.