Hydration and cooling in elite athletes: relationship with performance, body mass loss and body temperatures during the Doha 2019 IAAF World Athletics Championships

Purpose To characterise hydration, cooling, body mass loss, and core (T-core) and skin (T-sk) temperatures during World Athletics Championships in hot-humid conditions. Methods Marathon and race-walk (20 km and 50 km) athletes (n=83, 36 women) completed a pre-race questionnaire. Pre-race and post-race body weight (n=74), T-core (n=56) and T-sk (n=49; thermography) were measured. Results Most athletes (93%) had a pre-planned drinking strategy (electrolytes (83%), carbohydrates (81%)) while ice slurry was less common (11%; p<0.001). More men than women relied on electrolytes and carbohydrates (91%-93% vs 67%-72%, p <= 0.029). Drinking strategies were based on personal experience (91%) rather than external sources (p<0.001). Most athletes (80%) planned pre-cooling (ice vests (53%), cold towels (45%), neck collars (21%) and ice slurry (21%)) and/or mid-cooling (93%; head/face dousing (65%) and cold water ingestion (52%)). Menthol usage was negligible (1%-2%). Pre-race T-core was lower in athletes using ice vests (37.5 degrees C +/- 0.4 degrees C vs 37.8 degrees C +/- 0.3 degrees C, p=0.024). T-core (pre-race 37.7 degrees C +/- 0.3 degrees C, post-race 39.6 degrees C +/- 0.6 degrees C) was independent of event, ranking or performance (p >= 0.225). Pre-race T-sk was correlated with faster race completion (r=0.32, p=0.046) and was higher in non-finishers (did not finish (DNF); 33.8 degrees C +/- 0.9 degrees C vs 32.6 degrees C +/- 1.4 degrees C, p=0.017). Body mass loss was higher in men than women (-2.8 +/- 1.5% vs -1.3 +/- 1.6%, p<0.001), although not associated with performance. Conclusion Most athletes' hydration strategies were pre-planned based on personal experience. Ice vests were the most adopted pre-cooling strategy and the only one minimising T-core, suggesting that event organisers should be cognisant of logistics (ie, freezers). Dehydration was moderate and unrelated to performance. Pre-race T-sk was related to performance and DNF, suggesting that T-sk modulation should be incorporated into pre-race strategies.