Increased risk of heat stress conditions during the 2022 Comrades Marathon

Abstract

The Comrades Marathon is South Africa’s – and the world’s – most recognised and largest ultra-marathon event, with over 15 000 participants from across the globe competing in the 89-km road running event each year. Historically, the event has been held before the start of austral winter (20 May – 17 June). However, in 2022, organisers of the race moved the event to 28 August, when austral spring commences. We explore the climate, in particular the Universal Thermal Comfort Index (UTCI), of past Comrades events (1980-2019) and compare these data to UTCI data of the new proposed date (28 August) for the same period. The climatology for May, June, July and August was determined to identify periods with the lowest risk for ‘strong’ to ‘very strong’ heat stress. Results show that participants’ risk of exposure to ‘strong’ heat stress and ‘very strong’ heat stress periods will be more likely if the event is held in August as compared to the original event dates. Therefore, it is concluded that mid-June to mid-July has the lowest risk of heat stress exposure along the route. Runners and organisers should be aware of the higher risk of exertional heat illness during the 2022 Comrades Marathon to ensure safe participation.

Comment on Havenga et al. (2022): Standard heat stress indices may not be appropriate for assessing marathons

“…There are no days when the UTCI indicates 'extreme' heat stress. Using PET (1), there are more days in August than in May on which PET indicates 'strong' heat stress, and no days when the PET indicates 'extreme' heat stress. Using PET(2), there are more days in May than in August on which the PET indicates 'strong' or 'extreme' heat stress.…”

“…Using PET(2), there are more days in May than in August on which the PET indicates 'strong' or 'extreme' heat stress. Therefore, UTCI and PET (1) indicate that May has lower heat stress, but PET (2) indicates that August has lower heat stress.…”

“…Havenga et al 1 justified their use of UTCI with reference to other studies, but these other studies do not provide a strong justification for using UTCI. One reference related to the thermal comfort of spectators, rather than competitors.…”

“…While Havenga et al 1 are right to examine the thermal environment of the Comrades Marathon, the Universal Thermal Climate Index (UTCI) might not be an appropriate metric. When the thermal environment is simplified into a single index, choices about the relative importance of temperature, humidity, wind, and radiative temperature are codified.…”

“…None of these studies demonstrates that UTCI is uniquely appropriate for thermal evaluation of distance running, and other research has highlighted these limitations for the sports context. 3 The limitations of UTCI are acknowledged by its developers 8 but Havenga et al 1 do not discuss how these limitations affect their results.…”