MGMIMass Gathering Medicine

← Library

AI-DRAFTED — PHYSICIAN REVIEW IN PROGRESSThe citation for this entry was checked against Crossref and PubMed, but its summary and interpretation were drafted by an AI model from the published abstract and have not yet been individually read by a physician. Read the linked source before relying on this operationally.
Paper ✓ verified

What do thermal indices lack to help predict heat-related risk in elite Athletics?[1]

Bandiera D, Garrandes F, Kowalski J, Adami PE, Racinais S, Matzarakis A, Pitsiladis YP, Tessitore A, Bermon S · 2026 · Br J Sports Med

Summary

Retrospective analysis of 4938 athletes across 80 World Athletics races held 2019-2024 in five endurance disciplines (long-distance track, marathon, racewalking, cross-country, trail-running), testing how well environmental, individual and race variables predict exertional heat stroke (EHS), did-not-finish (DNF) and medical-encounter (MED) outcomes - with particular attention to the wet bulb globe temperature (WBGT), the thermal index international federations rely on. EHS frequency averaged 8/1000 and rose to 16/1000 when WBGT exceeded 28.0 degrees C, independent of sex (p=0.297) or discipline (p=0.980). DNF and MED were higher in marathon, racewalking and trail-running than in shorter disciplines (p<0.001). Of the environmental variables, mean radiant temperature had the strongest univariable association with EHS (R2=0.11, p<0.001) while WBGT was weaker (R2=0.04, p=0.018); overall predictive accuracy was limited (best model error 0.5 +/- 0.7 EHS per race). The authors conclude that neither WBGT nor radiant temperature predicts heat risk well enough on its own and that future models should add heat acclimatisation and recent illness.

So what

A direct audit of the instrument event medical plans lean on to set heat policy. WBGT is the number that triggers start-time shifts, extra cooling and cancellation thresholds - and here it explains only about 4% of the variance in EHS (R2=0.04), with the sun-load term (mean radiant temperature) doing better but still weakly. The planning lesson is not to discard WBGT but to stop treating a single index crossing a cut-off as a reliable predictor: a WBGT-only escalation rule will both miss hot-but-low-WBGT days and over-call, and radiant/solar load deserves its own line in the risk assessment. It also strengthens the field's move toward multi-factor heat triggers (acclimatisation status, recent illness, discipline/duration) rather than one thermometer, and confirms the endurance disciplines (marathon, racewalk, trail) as the high-yield ones. Caveat: elite athletes, not spectators, and EHS specifically - not the general medical-encounter load a mixed event generates; cite for the prediction limitation, not for population rates.

Key findings

  • 4938 athletes, 80 World Athletics races 2019-2024, 5 endurance disciplines
  • EHS 8/1000 average; 16/1000 when WBGT >28.0 C; independent of sex and discipline
  • DNF and MED higher in marathon/racewalking/trail than shorter events (p<0.001)
  • Mean radiant temperature strongest single predictor of EHS (R2=0.11) but WBGT weaker (R2=0.04, p=0.018); predictive accuracy limited overall
  • WBGT alone is an insufficient heat-risk predictor - add radiant/solar load, acclimatisation and recent illness (cf. threshold-triggers + weather pages)

Read the paper