World Athletics (WA) today introduced its much-anticipated “amended” running-shoe rule, and it’s essentially a broadside against the Nike Alphafly shoe that Eliud Kipchoge wore last October in his exhibition 1:59:40 marathon in Vienna.

The new rule, to take effect immediately, requires that running shoes have a maximum midsole thickness of 40 mm and no more than one stiff plate. This rule appears to grandfather the Nike Next% shoe that Bridgid Kosgei wore to her world-record 2:14:04 in the Chicago Marathon last fall.

The new rule, however, wouldn’t permit elite runners to wear the Alphafly, which is believed to have a midsole exceeding 40mm and more than one plate. A number of Nike runners may have been preparing to wear the Alphafly in the Feb. 29 U.S. Olympic Marathon Trials in Atlanta. In a phone call on Friday, Susan Hazzard, Director of Public Relations for USATF, said, “USATF has and will continue to follow all World Athletics and IOC rules.”

The competition manager at any race will have the right to confiscate, post-finish line, any shoes he/she believes to be questionable. These shoes could then be measured for midsole thickness, and presumably sawn in half to assess the number of plates.

“It is our duty to preserve the integrity of elite competition,” said WA president Sebastian Coe, long associated with Nike. “As we enter the Olympic year, we can draw a line by prohibiting the use of shoes that go further than what is currently on the market.”

Brooks Hyperion Elite Carbon-plate Shoe

Brooks Hyperion Elite comes out February 27 — so will be eligible for Tokyo / photo 101 Degrees WestThe new rule also addresses the “widely available” side of the equation. It states that after April 30, 2020, no shoe can be used in competition unless it is “has been available for purchase by any athlete on the open retail market” for at least four months. This means that new shoes in the Tokyo Olympics must be available by about March 15.

A shoe that does not meet this criterion will be termed a “prototype,” and prototypes will not be legal. Three Nike runners famously wore prototype Vaporfly 4% shoes in the 2016 Olympic Marathon Trials, and the first three finishers in the Rio Men’s Marathon likewise wore Vaporfly prototypes. With its new rule, WA is clearly trying to avoid a repeat of 2016.

The new rule will satisfy those who desired a restrictive shoe rule to keep record performances from continuing to fall at their recent rapid clip. On the other hand, many others favored an approach of unfettered innovation, and wonder if these limitations will make a difference or if designers will simply find ways to improve shoes within the new parameters.

Many questions remain:

One outstanding question: What’s the definition of “available?” Six pairs, or 10,000?

Several known prototypes may not be legal in Tokyo, such as the Saucony Endorphin Pro, not slated to be available until June 1 (which has already been worn in competition by runners like Jared Ward, Parker Stinson and Molly Huddle). And what of New Balance’s prototype that Emily Sisson reportedly plans to wear in Atlanta with no stated public release date? The Brooks Hyperion Elite, scheduled to be released February 27, should be in the clear. Might other manufacturers move up their release dates to comply with the ruling?

Another question: Could Nike or a Nike athlete lodge a protest with the Court of Arbitration for Sport? And what will the World Marathon Majors decide?