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

Abstract

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°C±0.4°C vs 37.8°C±0.3°C, p=0.024). T_core (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 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°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 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.

Keywords: thermoregulation.

Figure 1

Drinking strategy during the World Athletics Championships. Left panel: percentage of athletes declaring to include the described drink in their strategy. Right panel: drink quantity planned by race (in % of athletes). *P<0.05. 20KRW, 20 km race-walk; 50KRW, 50 km race-walk.

Figure 2

Pre-cooling and mid-cooling strategy during the World Athletics Championships. Upper panel: percentage of athletes declaring to plan a pre/mid-cooling strategy. Lower panel: details of the strategy declared (in per cent of athletes). Right panel: example of water dousing plus neck collar, and ice in cap with neck flap. Getty images for World Athletics.

Figure 3

Core and skin temperature in finishers, disqualified and did not finish (DNF). Pre-race skin temperature was correlated to the relative finishing time (in % if personal best, r=0.32, p=0.046). DNF had a higher pre-race skin temperature than finishers (*p=0.017). Square, diamond and triangle represent marathon, 20 km and 50 km race-walks, respectively. Blue and pink symbols represent men and women, respectively. %PB, percentage of personal best.

Figure 4

Example of different pre-cooling strategies and their repercussion on pre-race skin temperature.

Figure 5

Individual body mass variation from pre-race to post-race. Values in percentage of pre-race body mass. 20KRW, 20 km race-walk; 50KRW, 50 km race-walk.