Hydration and cooling in elite athletes. Relationship with performance, body mass loss and body temperatures during the Doha 2019 IAAF world athletics championships. British journal of sports medicine

Purpose To characterise hydration, cooling, body mass loss, and core (Tcore ) and skin (Tsk ) 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), Tcore (n=56) and Tsk (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 Tcore was lower in athletes using ice vests (37.5°C±0.4°C vs 37.8°C±0.3°C, p=0.024). Tcore (pre- race 37.7°C±0.3°C, post- race 39.6°C±0.6°C) was independent of event, ranking or performance (p≥0.225). Pre- race Tsk was correlated with faster race completion (r=0.32, p=0.046) and was higher in non- finishers (did not finish (DNF); 33.8°C±0.9°C vs 32.6°C±1.4°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 Tcore , suggesting that event organisers should be cognisant of logistics (ie, freezers). Dehydration was moderate and unrelated to performance. Pre-race Tsk was related to performance and DNF, suggesting that Tsk modulation should be incorporated into pre- race strategies.