Microclimate variation and estimated heat stress of runners in the 2020 Tokyo Olympic Marathon

Eichi Kosaka, Akiko Iida, Jennifer Vanos, Ariane Middel, Makoto Yokohari, Robert Brown

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


The Tokyo 2020 Olympic Games will be held in July and August. As these are the hottest months in Tokyo, the risk of heat stress to athletes and spectators in outdoor sporting events is a serious concern. This study focuses on the marathon races, which are held outside for a prolonged time, and evaluates the potential heat stress of marathon runners using the COMFA (COMfort FormulA) Human Heat Balance (HBB) Model. The study applies a four-step procedure: (a) measure the thermal environment along the marathon course; (b) estimate heat stress on runners by applying COMFA; (c) identify locations where runners may be exposed to extreme heat stress; and (d) discuss measures to mitigate the heat stress on runners. On clear sunny days, the entire course is rated as 'dangerous' or 'extremely dangerous', and within the latter half of the course, there is a 10-km portion where values continuously exceed the extremely dangerous level. Findings illustrate which stretches have the highest need for mitigation measures, such as starting the race one hour earlier, allowing runners to run in the shade of buildings or making use of urban greenery including expanding the tree canopy.

Original languageEnglish (US)
Article number192
Issue number5
StatePublished - May 17 2018
Externally publishedYes


  • COMFA Human Heat Balance Model
  • Heat stress
  • Marathon games
  • Tokyo 2020 Olympic Games
  • Urban microclimate

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)


Dive into the research topics of 'Microclimate variation and estimated heat stress of runners in the 2020 Tokyo Olympic Marathon'. Together they form a unique fingerprint.

Cite this