Nike's VaporFly shoes, which are clearly identified in races due to their bright green and pink hues, have been at the heart of controversy since 2016, when many sponsored runners participated in prototypes at the US Olympic marathon trials and later at the Rio de Janeiro Olympics. The shoes were said to be more responsive and less prone to blisters than traditional footwear, thanks to a new vaporization system that released moisture away from the foot during exercise. The technology was initially tested by Nike on its World Marathon Majors series in 2015, where two winners wore the shoes: Lornah Kiplagat (then aged 30) who claimed her first title in Tokyo, and Zersenay Tadese of Ethiopia who took home the trophy in Dubai. However, some athletes raised concerns about injuries caused by the lack of any form of cushioning inside the shoe, as well as doubts over how the technology would perform in warmer climates like those found in Asia and Africa. As a result, Nike withdrew the shoes from competition until after the Olympics, when they were made available to the public. Several runners including Dennis Kimetto and Eliud Kipchoge used them to win gold and silver medals respectively at the Rio Games. But questions remain over whether they actually helped these athletes run faster, with some experts claiming they may have hindered them instead.