For 17 months at the end of the 2000s, swimming went through a golden age. Between 2008 and 2009, more than 130 world records, across all distances and strokes, were smashed. American swimmer Michael Phelps was in his prime, and after the 2008 Beijing Olympics there were only four events – the men's 400- and 1,500-metre freestyle and women's 100-metre breaststroke and butterfly – that survived the world record onslaught.To buy more nike free run sale with cheap price, you can visit shoes2021.com official website.

Many of the records set in this period still remain today, with swimmers unable to match the performances of the previous generation. But the brief period of success was mired in controversy.

Swimming's record-breaking months were largely down to Speedo. The company's LZR Racer swimsuit line, which hit the market in February 2008, covered almost all of a swimmer's exposed skin and compressed the body into a more streamlined shape. The polyurethane-based material also trapped air, giving extra buoyancy.

The swimsuits sparked an arms race between sport manufacturers: Speedo’s rivals rushed to create their own similar suits, each wanting to give athletes an extra edge. Swimming's governing body, FINA, was caught out by the rapid technological progress. “The regulations that FINA had in place at the time didn't anticipate some of the technological advances that particularly Speedo and other brands were driving,” says Mike Caine, a professor of sport technology and innovation at Loughborough University.

By the time it came to swimming's world championships in 2009, FINA had stepped up to questions raised around the ethics of using high-tech swimsuits to obliterate the previous best efforts of humans. The governing body tested almost 400 models of swimsuits and approved 202 for use in the event. At the start of 2010, it introduced new regulations on the coverage and materials of suits, effectively banning the performance-enhancing technologies.

Over the last three years, a similar situation has crescendoed in competitive running. The new culprit? Nike's Vaporfly trainers.

The Vaporfly shoes include a carbon fibre plate and a wedge of soft, energy-returning foam that help runners move at least four per cent more efficiently. The claim was first made by Nike but has since been backed-up by academic studies. The shoes, first introduced in 2016 and currently in their third iteration (with a fourth at a prototype stage), have been worn to break multiple world records and are seen on the feet of the leading runners in races ranging from five kilometres to road-based ultramarathons. Only now, three years after the Vaporfly trainers first emerged, are running shoe rivals releasing their own versions of footwear with carbon fibre plates installed.

But the success of Nike's trainers has divided the running community. Critics of the shoe say they enhance human performance beyond iterative advancements and amount to “technological doping”, while fans can’t get enough of them. Now, ahead of the Tokyo Olympics this summer, running's governing body World Athletics has intervened, publishing new rules on what is allowed from running shoes.The rules state that, from April 30, any shoe must have been available for purchase for four months before it can be used in competitions, and prototypes cannot be used during races. More significantly, World Athletics ruled that Nike's Vaporfly shoes and records broken using them are legal, but that an upcoming pair of AlphaFly trainers being trialled won't be allowed in the Olympics due to the thickness of their soles. The new rules state that soles can't be thicker than 40 millimetres and can't contain more than one piece of carbon fibre (or other rigid material) in the form of a plate.