Japanese athletics officials on Tuesday slammed the decision to move the 2020 Olympic marathon and race-walking events from Tokyo to Sapporo, saying the move did not put competitor interests first.
The IOC ordered the move last month after seeing athletes struggle to cope with hot and humid conditions at the world championships in Doha in September.
"The IOC was shocked by what we saw in Doha in very similar conditions in terms of temperature and humidity to what's expected here in Tokyo," John Coates, head of the body's coordination commission, said at the time of the announcement.
The IOC had a responsibility "to always put the health of athletes first", he said.
The announcement caught Tokyo 2020 organisers by surprise, and on Tuesday Kazunori Asaba - training chief of the Japan Association of Athletics Federations (JAAF) - told reporters it should never have been made.
"It's like the athletes who had been training for many years to climb Everest were told just nine months before they would go to a different mountain," he said.
The decision "does not put athletes first in a real sense", he added. "From the perspective of training... 'athletes first' means not wasting their efforts."
Dozens of competitors were affected or needed medical attention as hot and humid conditions took their toll in the ultra-distance events at the Doha world championships.
JAAF marathon director Tadasu Kawano disagreed, however, saying the athletes in Doha did not complain and tried their best.
"The athletes are not joining competitions to be protected," he said.
"It is their mission to make efforts within the rules that are already set and compete by manifesting superhuman abilities."
The Tokyo government last week accepted the IOC decision, saying it was effectively out of their hands.