Nike's CEO joked the brand's controversial Vaporfly running shoes help him walk faster at work

• Nike's boss joked its controversial Vaporfly running shoes help him walk faster at work.
• "The time it takes me to walk across the Nike campus here at headquarters has dropped by at least 4%," CEO Mark Parker said on the sportswear titan's earnings call this week.
• The Vaporfly line has drawn criticism for providing an "unfair" advantage - Kenyan runner Eliud Kipchoge wore a pair to complete an unofficial marathon in less than two hours in October.
• View Business Insider's homepage for more stories.

Nike's boss joked the sportswear titan's controversial Vaporfly running shoes help him walk faster at work.

"The time it takes me to walk across the NIKE campus here at headquarters has dropped by at least 4%," Mark Parker replied to an analyst's question this week about how much faster he runs with the shoes. "Feels really good."

Nike markets the Vaporfly 4% as offering "4% greater efficiency than our previous fastest running shoe," meaning runners use 4% less energy while wearing them. It pitches the newer Vaporfly Next% as "the fastest shoe we've ever made."

Critics have attacked Vaporfly shoes as unfair and a form of "technology doping" because they appear to give wearers a distinct advantage over competitors. They warn that race winners might not be the the fastest or fittest, but those with the best footwear.

The New York Times analyzed about 500,000 marathon and half-marathon running times between 2014 and 2018. It found that "runners in Vaporflys ran 3 to 4 percent faster than similar runners wearing other shoes, and more than 1 percent faster than the next-fastest racing shoe."

Kenyan runner Eliud Kipchoge - who broke the marathon world record with a time of 2:01:39 in September 2018 - wore a version of the shoes to complete an unofficial marathon in less than two hours in Vienna two months ago.

Similarly, Nigerian runner Brigid Kosgei wore them to run the Chicago marathon in 2:14:04 in October, shaving 81 seconds off the previous women's world record.