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Larner tests heat and humidity on Tokyo Olympic marathon course one year out

Brett Larner of Japan Running News has been out running the Olympic marathon course in Tokyo at 6 am to find out exactly how hot and humid it's likely to be one year from now

Exactly one year out from the Tokyo 2020 marathon, the runner behind the popular Twitter account @JRNHeadlines (aka Japan Running News) has taken it upon himself to personally test the Tokyo 2020 marathon course for heat and humidity. Brett Larner ran a little more than 30K of the course at a steady pace of just under five minutes per kilometre on three different occasions, documenting heat and humidity along the way. His findings are sobering.

The women’s marathon will be run at 6:00 a.m. local time on Saturday, August 1, 2020, with the men’s race following one week later. Larner started at the same time, recording air temperature and humidity at half-hour intervals. The temperature fluctuated between 28.8 C just before he started his first run and 33 C at 9:30 a.m., with humidity falling from a high of 81 per cent at the start to 71 per cent at 9:30 a.m.

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This morning he headed out for a third, 23K run on the course with last year’s euro champs winner Koen Naert of Belgium.

Larner reports that it has been a relatively cool season by Tokyo standards, but since late July, following an extended rainy season, it has been extremely hot and humid. He says he was dripping with sweat and dizzy from exertion early in the run. Larner did this run a year ago, when the marathon was still scheduled to start at 7:00 a.m., and praises the decision to move it to 6, as well as the plan to provide misting stations and avoid direct sunlight on the course as much as possible.

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“…The last time Tokyo held the Olympics in the ’60s they were in the fall to avoid the heat,” Larner told us. “That’s no longer an option due to international TV broadcast constraints. Having run the course four times on the actual days and time the marathons will be held, I felt the toughest issue was exposure to direct sunlight, which would make a nighttime marathon seem like a good solution… That also seems to be off the table due to international TV broadcast demands. I’m skeptical that the heat-reducing pavement surface they’ve laid down on some of the east-west sections and the trees along some of those parts are going to do very much, but moving the start time to 6:00 a.m., routing most of the course on north-south roads to take advantage of shadows from buildings, and the mist stations they’re planning to put out are all good steps given the constraints they have to work with.”

Larner also reports seeing a number of the Japanese men who will likely contest the marathon out on the course, including 2018 Fukuoka Marathon winner Yuma Hattori, hoping to give themselves an edge and capitalize on the home advantage.

Larner plans to be back out on the course again on Friday, one year out from the men’s Olympic marathon.