The shoes came in the colors of a tropical drink, lime and orange and pink, as if the logo ought to be an umbrella instead of a Nike swoosh. You half expected the insoles to smell of rum and coconut.
If the color scheme suggested frivolity, race results did not. The shoes cushioned the feet of all three medalists in the men’s marathon at the Rio Olympics last summer. Later, in the fall, they were worn by the winners of major marathons in Berlin, Chicago and New York.
The latest shoe designs have produced fast times and impressive results in international races. But they have also spurred yet another debate about the advance of technology and the gray area where innovation meets extremely vague rules about what is considered unfair performance enhancement for the feet.
Where to draw the line of permissible assistance?
Many sports have struggled with the answer. Swimming allowed record-setting, full-body suits, then banned them after the 2008 Beijing Olympics because they gave an unfair advantage in buoyancy and speed. And track and field wrestled with the issue of prosthetic blades worn by the South African sprinter Oscar Pistorius.
The latest issue is shoes. Track’s governing body, the International Association of Athletics Federations, said in an email that it had received a number of inquiries about elite runners’ wearing new designs made by various companies. Its technical committee will meet within two weeks to “see if we need to change or review approvals.”
Bret Schoolmeester, Nike’s senior director for global running footwear, said, “We’re very confident we’re doing things within the rules and above board.”
On Tuesday, Nike unveiled a new shoe, a customized version of the one worn by the marathon winners in Rio de Janeiro and other recent high-profile races, as part of the company’s bold — some say gimmicky — attempt to break two hours in the marathon in early May.
Adidas, whose shoes have been worn by the last four men to set the world marathon record, also recently unveiled a shoe for its own, less publicized attempt to lower the current record from 2 hours 2 minutes 57 seconds to 1:59:59 or faster.
George Hirsch, the chairman of New York Road Runners, which organizes the New York City Marathon and more than 50 other races, said everything from elite races to age-group competitions could be affected by the latest shoe technology. It would be impossible to check the shoes of hundreds or thousands of runners before each race, he said.
“This is a game changer, in the sense that if the shoe companies get patents and these shoes go onto the market, and they’re in wide use, it does make you wonder if it’ll be a level playing field if people can use these advantages,” Hirsch said.
All shoes are considered to enhance performance. Otherwise, everyone would run barefoot. But at what point is the line of inequitable advantage crossed? No one seems to know precisely.
“It’s quite a fun ethical sports technology area that we’re heading into,” said Ross Tucker, an exercise physiologist from South Africa who writes the Science of Sport, a blog that is widely followed in running circles.
When tennis rackets went from wood to metal, he said, “I bet they were having the same discussion.”