When wheelchair rugby was first invented in 1976, it was called murderball.
The sport has been part of the Paralympics since 1996 and is played with mixed-gender teams. The United States team was once dominant in the sport, winning gold in three of the first four Games where it was played, but Australia earned the top spot at both the 2012 and 2016 Paralympics.
The silver and bronze medals have bounced between a small group of other nations that includes Japan, New Zealand, Canada and Great Britain. All of those teams, plus the U.S., Australia, Denmark and France, will compete for gold at the Tokyo Paralympics, which began Tuesday.
Wheelchair rugby was created by a group of athletes who played wheelchair basketball but struggled with the technical shooting aspect of the game. Wheelchair rugby became an alternative. Team USA coach John Gumbert said anyone can succeed in the sport after he was recruited to play in 1992 with no prior experience by a stranger in a shopping mall.
"All the stereotypes of what I'm living with, in so many ways we have been told what we could and couldn't do," Gumbert said. "This sport really allows us to live and show the world what we can do. That's a powerful thing."
Here's everything you need to know to enjoy "murderball" during the Games:
What is wheelchair rugby?
The sport, according to the Canadian Paralympic Committee, combines elements of basketball, ice hockey and handball. The only similarity to traditional rugby is the name. It is played on a basketball court using a standard volleyball.
Wheelchair rugby is high-speed with few stoppages, and it is a full-contact sport that features lots of chair bumping and crashing, though there is no body contact allowed. There are also limitations on how and where athletes can crash into each other for safety reasons.
"When you see the sport, you're like, 'Oh my gosh,' because chair contact is legal and it's encouraged. That's what sells our sport, it's the full contact," said Gumbert. "From our humble beginnings in the early 80s, we're at a place now where ... the average athlete can get from one end of the court to the other in about five seconds, so they're flying and the hits are big."
What are the rules?
The wheelchair rugby court is divided into two halves with a center circle, and at the end of each half is a small area known as the key. It is played in four eight-minute quarters with four players on the court at a time.
The objective of the game is to have two wheels of the wheelchair cross the opposing team's goal line, which scores a point. Each possession has a 40 second "shot clock" in which a team must score or turn the ball over.
The ball must be dribbled every 10 seconds, and players on offense also cannot remain in the opposing team's key for more than 10 seconds. On defense, teams cannot have more than three players inside their key at one time.
Who can play?
Wheelchair rugby at the Paralympics can only be played by athletes with a certain level of physical impairment. Athletes with spinal cord injuries — the most common disability among players — must have impairments in at least three of their limbs. Athletes who do not have spinal cord injuries must have some degree of impairment in all four limbs.
"If I do my job as a coach, people will see that there is a way to play the sport, not that the athletes playing in it are confined to chairs," Gumbert said. "That's a huge breakthrough moment in adaptive sport because we want people to be able to say 'Wow, I wish I could play that sport,' and in our sport, it's happening."
Athletes undergo certain tests and observations before they are cleared to play and are given a numerical rating of their functional level on a scale from 0.5 to 3.5. The combined functional rating of a team may not exceed eight.
Who are the key players on the U.S. team?
Chuck Aoki is the star of Team USA. He has a genetic condition called hereditary sensory and autonomic neuropathies type II, which causes him not to have feeling in his body below the knees and elbows. He helped lead the U.S. team to a silver medal at the Rio de Janeiro Paralympics and a bronze in London. He was also the U.S.'s flag bearer at the Paralympic opening ceremony.
Gumbert said Aoki began as a wheelchair basketball player and has thrived since joining wheelchair rugby. Gumbert also said Joe Delagrave, who is a team captain alongside Aoki, is a key player to watch.
"He's an incredible leader on and off the court. His size is unmatched," he Gumbert said of Delagrave. "You can't teach size and Joey is the biggest guy on our team, so you'll see him in big moments out there."
When to watch Team USA
The U.S. kicked off the group stage of the Paralympic tournament Tuesday with a blowout win over New Zealand. The team will play the second game of the group state today at 10:30 p.m. ET against Canada and the final group game Aug. 27 at 4:30 a.m. ET against Great Britain.
The U.S. and Canada have a fierce rivalry in wheelchair basketball, and Gumbert said that will be a must-see matchup.
"You prepare for everything, every game, but looking forward, the next game is a big game against Canada," he said. "We could play Canada in a parking lot behind a zoo with nobody there and it would be just fine with us. We really enjoy the the rivalry."
If Team USA advances, it will play in the semifinals Aug. 28 and both medal matches are on Aug. 29.
Contact Emily Adams at email@example.com or on Twitter @eaadams6.
This article originally appeared on USA TODAY: Paralympics: What is wheelchair rugby, a sport once called murderball?