TOKYO, July 28 (Reuters) - A stack of Olympic and possibly world records will be broken on the Tokyo track over the next two weeks but, such has been the incredible impact of shoe technology on performance lately, that nobody quite knows what constitutes great any more. It used to be the case the world records on the road and track were edged down by fractions of a second, often untouched for years at a time, before the next generation shaved a couple of hundredths and were rightly feted. However, since the arrival of thick-soled, carbon-plated road shoes, and now their track spike equivalent, long-standing records set by the sport"s all-time greats are being obliterated, and then obliterated again, to leave historical comparisons difficult, if not impossible. Any lingering questions about how much difference Nike"s Alphafly shoes made disappeared in one weekend in October, 2019 when Eliud Kipchoge wore them to run the first, unofficial, sub-two hour marathon and fellow Kenyan Brigid Kosgei lopped four minutes off her personal best to break Paula Radcliffe’s 16-year-old women’s marathon record by over a minute. On the roads, 17 of the 20 fastest men"s marathon times in history have been set in the last five years and, coincidentally, it is the same case for women over the distance. Nobody had gone under 58 minutes for the half marathon until last December when four men did in the same race - with winner Kibiwott Kandie clocking an amazing 57 minutes 32 seconds in his Adidas Adios Pro carbon shoes. As that technology filtered into track spikes, Uganda"s Joshua Cheptegei destroyed the early 2000s world records of all-time-great Kenenisa Bekele in the 5,000m and 10,000m. Last month Dutchwoman Sifan Hassan took a huge 10 seconds off the 10,000m world record but even that giant leap lasted all of two days as Ethiopia’s Letesenbet Gidey beat it by another five seconds. The effect is not being felt only over long distances, either. Elliot Giles smashed Sebastian Coe"s British indoor 800m record this year as his 1:43.62 became the second-fastest of all time. Jamie Webb, who also bettered Coe"s mark in normal spikes in the same race, explained how he was "stunned" when he first tried the new technology. "You feel a sense of propulsion when you run in them and they allow you to run with more efficiency and stay on at the end of a race," he told The Times. "I stopped using the shoes because they made it difficult to measure myself against previous training sessions. But I will use them in races as I will be putting myself at a disadvantage if I don"t." ELITE LEVEL The impact is not being seen only at elite level. In the six years between 2013 and 2019 a total of five athletes went under 29 minutes in America"s National Collegiate Championships 10,000 metres. In this year"s race the first 10 were sub-29, all of them inside the 42-year-old meeting record. American students Cooper Teare and Cole both ran 3.50 for the mile in a February indoor race and found themselves improbably catapulted into the top 10 of all time, slipping in just ahead of Olympic champion Matt Centrowitz and former world record holder Noureddine Morceli. World Athletics (WA), the sport"s governing body, finally got around to introducing limits to the thickness of foam and number of plates allowed in road shoes and spikes at the end of 2020. Discussions with biomechanical experts and industry representatives are continuing with a view to further regulation. But with the shoe companies, particularly Nike, providing the vast majority of the sport"s funding and WA saying they are seeking a compromise that "does not stifle innovation" the genie is seemingly out of the bottle for good. "It concerns me greatly that the sport is going to lose context with its all-time great performances, including the 800m world record," said James Templeton, agent of Kenyan David Rudisha, who set that mark in one of the great races of the 2012 Olympics. Some frustrated observers are demanding a "year zero" approach, as was introduced when changes to the design of javelins meant that records began anew with the refined implement but for now, fans are going be left struggling to comprehend what they are watching. "Forget what you think you know," said Geoff Burns, a biomechanics expert at the University of Michigan. "We just have to stop getting excited about fast times, because everything has changed."