91Èȱ¬

A pair of running shoes have caused quite a stir in the sporting world.

One of Nike's ranges has come under fire with claims that the Vaporfly shoe, famously worn by Eliud Kipchoge in his record-breaking marathon run last year, gives runners an unfair advantage.

Under current World Athletics rules, shoes can't be made in a way that provides athletes with an upper hand over their competition. Any shoes worn must also be available to all other competitors.

World Athletics, the governing body for the sport, says it will be tightening the rules around high-tech running shoes.

The shoes are made from a very lightweight material and contain a extra-springy foam and a carbon plate which is said to help propel wearers forward.

Nike says their shoes can improve a runner's efficiency by 4%.

The Vaporflys aren't the only example of controversial tech in sport. Here's some other tech that caused a bit of a storm in the sports world.

FINA, the international body that governs swimming, banned full-body high-tech swimsuits made of polyurethane from competitions back in 2010.

Speedo was one of the most popular makers of the suits and likened them to shark skin. The swimsuits were made to reduce the drag on swimmers' body as they travelled through the water, making them go faster.

Officials decided to ban athletes from wearing the polyurethane suits after an extraordinary number of records were smashed following their introduction back in 2008.

28-time Olympic medallist Michael Phelps secured eight gold medals at the Beijing Olympics wearing Speedo's LZR Racer suit and in 2009, 29 new world records were set in the first five days at the World Swimming Championships in Rome. The majority of the the athletes who broke records were wearing polyurethane suits.

Cyclist Chris Boardman won the 4km pursuit at the Olympic Games in 1992. Before his triumph at the games, Great Britain had failed to win a gold medal in the event for 72 years.

Boardman won the race with a bike created by Lotus Engineering which was the first of its kind.

It had forward pointing handlebars and a solid back wheel which proved very controversial - now they're standard.

Adidas' Predator football boots were designed by former footballer, Craig Johnston.

The South African, who was brought up in Australia, thought up the idea when he was thinking of ways to help the children he was coaching improve their ball control.

The trainers, first introduced in 1994, included rubber ridges on the front which Johnston claimed would help players to swerve the ball more easily.

The material used on the heads of curling brooms has changed - a lot - over the years.

Before 2015, many top players opted for fabrics that scratched the ice. Players would use the scratches to steer 'the rock' after the throw, giving them an advantage.

This was later ruled to be unfair and by 2016 all fabrics that caused scratches to the ice were banned.