Fionnuala McCormack regrets the decision of World Athletics to permit the use of the controversial Nike Vaporfly running shoes for the 2020 Olympics. 

World Athletics announced changes to its rules on Friday, outlawing some variants of running shoes and introducing strict limits to the technology developed for any future shoes used in elite competition.

The sport's governing body said that with immediate effect, road shoes must have soles no thicker than 40mm and not contain more than one rigid, embedded plate. The new regulations state that any shoe must have been available to purchase on open retail four months before its usage in competition. 

Thus, the Alphafly shoes used by Eliud Kipchoge to run the first sub-2 hour marathon in Vienna in October have been outlawed. 

However, the Nike Vaporfly - both 4% and Next% models - remain legal, and the records clocked by athletes wearing them remain in the books. 

Nike's shoes contain a carbon-fibre plate and energy returning foam that claim to increase long-distance running efficiency by 4%.

McCormack, who secured qualification for Tokyo with fifth place at the Chicago Marathon last October, is disappointed by the governing body's response, believing they should have been stronger in outlawing the Nike Vaporfly shoes.

"I'm not a fan of the shoes," McCormack told Game On on RTÉ 2fm. 

"I wish it never happened. I wish they'd been strong and put proper regulations down when they came out with their findings.

"I don't want to have to try them. I don't know what position I'm in now. You're not competing on a level playing field if you don't have the same shoes. But I don't want to have to wear them shoes.

"I'm not a fan of technology in running because I like it as it is. I suppose it's more pure.

"For me, I would question my times if I wore the shoes. I would have before and after (the shoes) times. But I suppose everyone else doesn't have that."

McCormack's Chicago run saw her shave four minutes off her personal best, clocking a time of 2:26:47

This saw her leap above Carey May and Sonia O'Sullivan to second place in the all-time list of Irish women marathon runners. 

"I would like to get the improvement out of training and not out of technology. I know there's probably things I did wrong in the race or things I could have changed around. Or more training.  

"I know I haven't maxed out. I know I can improve. I know where I can improve."

McCormack made her Olympic debut in Beijing in 2008, then Fionnuala Brittan and competing in the steeplechase.

For her fourth Olympics, the marathon has been moved to Sapporo to avoid the 'sweltering heat' in the Japanese capital. 

"I think it's a strange move. If I go to this Olympics, it'll be my fourth one. I've been in Olympic villages and experienced the stadiums. And it would be nice to experience all that again.

"But for athletes, where it's their first Olympics, it's very hard because I don't know how it can be an Olympic experience when you're that far away from everyone else. 

"And for the people of Tokyo, I feel it's a bit hard on them. Because the marathon is massive in Japan. They're going to hand their city over to the Olympics and to people all over the world for two or three weeks.

"And the one event that they can just walk onto the street and take part and watch is being taken away from them. It seems unfair."