IOC sports director Kit McConnell said the Executive Board had rubber-stamped a proposal to hold the men's and women's triathlon races at Odaiba Marine Park at 6:30am, an hour earlier than initially planned.

The same alteration has been made to the mixed relay, which will be held from 7:30am instead of 8:30am.

The cross-country section of the equestrian event will start between 7:30am and 8am with a view to finishing before 11am, which McConnell said was the cut-off point to protect the welfare of the horses.

The changes have been made amid concerns of the expected extreme heat in Tokyo.

Calls have grown in recent weeks to move the open water swimming event from its current location of Odaiba because of concerns regarding the water temperature, which crept towards the International Swimming Federation (FINA) limit of 31 degrees celsius during the summer.

McConnell claimed the data and information "isn't there for us to make that compelling case to bring the start time forward" at Tokyo 2020.

He said the IOC and Tokyo 2020 would only consider doing so once it received data to suggest it would be necessary to make the change.

McConnell also dismissed any chance of moving the open water swimming races out of the Japanese capital, following the controversial switch of the marathons and race walks from Tokyo to Sapporo.

The start time of other events, including the mountain bike races, have been changed to avoid the worst of the heat.