Roller derby is a bit like rugby - only indoor, and without a ball.
Anna-Ivy Bates, 29, who was brought up in Rotorua, is now living in Melbourne where she is a jammer for the world no 1 ranked Victorian Roller Derby League All Stars.
It is the first time a team from outside the United States has held the ranking.
Bates, whose derby name is Ivy K'nivey, was born and raised in Rotorua and went to Lynmore Primary, Rotorua Intermediate and Rotorua Lakes High School.
It was after she left school and went to Otago Polytechnic that she joined the ranks of the Freshmeat Roller Derby Women of Dunedin.
"I started with a pair of roller skates to get from A to B, travelling around Dunedin. Then I met someone at a party and they said 'you should try out roller derby'. I had already seen the Christchurch girls."
Bates said there were similarities with rugby - although there was no ball. Each team has a jammer and four blockers on the track with the jammers trying to lap the pack and the blockers trying to stop the opposing team's jammer.
"I always wanted to play rugby as a kid - maybe I was too little to play," said Bates.
"Roller skating involves more speed than you can get running, so it's about having speed, but there's also a lot of tactics and you are trying to outsmart them, trying to get through the pack, mostly unscathed.
"You want to minimise the number of laps they get and you want to get as many laps in as you can."
Players can be sent to the penalty box. High and various other types of blocks are illegal.
"Anything up high on the face, if you hit someone in the back to the ground or take out someone's feet. Above the knees to below the collar bone is the legal contact zone on the front, but you can't use your hands," said Bates.
"Like tackling, you use your whole body to move people out of the way or block people."
Each team has several jammers. Each jam, or section of the game, lasts a maximum of two minutes and each jammer goes on track every three to five jams.
"It's high intensity with explosive speed that you need for a short length of time."
Bates said she liked to think her Kiwi determination had kept her moving towards the top of her sport.
"It's what makes me want to be the best jammer I can possibly be and I like challenging myself to aspire to be the top."
After graduating from Otago, Bates didn't have any firm plans.
"I'd heard things about Melbourne and that they'd got a well-established roller derby team so I thought I'd head over there to see what it was like. I never imagined I'd still be there six years later."
World rankings come from playing other world teams - more often than not in tournaments in the US.
It isn't simply a case of winning games, but of minimising the number of laps the opposition complete.
Bates was part of Team New Zealand that competed in the World Cup in Texas two years ago and is also in the training squad for the next world cup in Manchester in 2018.