Association between thermal responses, medical events, performance, heat acclimation and health status in male and female elite athletes during the 2019 Doha World Athletics Championships

Purpose To determine associations between thermal responses, medical events, performance, heat acclimation and health status during a World Athletics Championships in hot-humid conditions. Methods From 305 marathon and race-walk starters, 83 completed a preparticipation questionnaire on health and acclimation. Core (T-core; ingestible pill) and skin (T-skin; thermal camera) temperatures were measured in-competition in 56 and 107 athletes, respectively. 70 in-race medical events were analysed retrospectively. Performance (% personal best) and did not finish (DNF) were extracted from official results. Results Peak T-core during competition reached 39.6 degrees C +/- 0.6 degrees C (maximum 41.1 degrees C). T-skin decreased from 32.2 degrees C +/- 1.3 degrees C to 31.0 degrees C +/- 1.4 degrees C during the races (p<0.001). T-core was not related to DNF (25% of starters) or medical events (p >= 0.150), whereas T-skin, T-skin rate of decrease and T-core-to-T-skin gradient were (p <= 0.029). A third of the athletes reported symptoms in the 10 days preceding the event, mainly insomnia, diarrhoea and stomach pain, with diarrhoea (9% of athletes) increasing the risk of in-race medical events (71% vs 17%, p<0.001). Athletes (63%) who performed 5-30 days heat acclimation before the competition: ranked better (18 +/- 13 vs 28 +/- 13, p=0.009), displayed a lower peak T-core (39.4 degrees C +/- 0.4 degrees C vs 39.8 degrees C +/- 0.7 degrees C, p=0.044) and larger in-race decrease in T-skin (-1.4 degrees C +/- 1.0 degrees C vs -0.9 degrees C +/- 1.2 degrees C, p=0.060), than non-acclimated athletes. Although not significant, they also showed lower DNF (19% vs 30%, p=0.273) and medical events (19% vs 32%, p=0.179). Conclusion T-skin, T-skin rate of decrease and T-core-to-T-skin gradient were important indicators of heat tolerance. While heat-acclimated athletes ranked better, recent diarrhoea represented a significant risk factor for DNF and in-race medical events.

Automated summary

This study investigates the associations between thermal responses, medical events, performance, heat acclimation, and health status in hot-humid conditions during a World Athletics Championships. It finds that skin temperature, the rate of skin temperature decrease, and the gradient between core and skin temperature are important indicators of heat tolerance. Athletes who underwent heat acclimation performed better, while recent diarrhea increased the risk of not finishing the race and experiencing medical events.