Measures to combat the heat in the Japanese capital, including better shade and water sprays, have been trialled at test events this summer.

International Olympic Committee president Thomas Bach said athlete welfare was "at the heart" of changes.

Sapporo can be as much as six degrees cooler than Tokyo in peak summer.

The plans will be discussed by the IOC at the end of the month as part of a special session on "heat countermeasures".

International Association of Athletics Federations president Lord Coe said: "Giving athletes the best platform for their performances within the environment they are in is central to all major events, and we will work with the organisers to create the very best marathon and race walk courses for next year's Olympic Games."

Tokyo 2020 event planned changes

• Athletics - longer distance races scheduled in the evening sessions only; earlier start times for marathon and race walk events.
• Rugby sevens - all morning games scheduled to finish before noon local time.
• Cycling - mountain bike start time delayed to 15:00