Beverage temperatures at aid stations : Port Macquarie Ironman

Background: Beverage temperature is known to effect palatability, fluid volume consumption and performance when athletes exercise for long durations, especially in the heat. Athletes anecdotally report that aid station beverage temperature ranges widely and is often unpalatable (22–30 °C) when competing in endurance events. No field study has reported on aid station beverage temperatures.

Method: Data was collected at the Port Macquarie Ironman from 0800 to 1800 h. Environmental temperature (mean and range or SD) was measured every 30 min and beverage temperature (mean and SD) every 10 min. Three locations on the cycle and two on the run course were monitored. Temperature of drink bottles with (n = 4) or without (n = 4) a temperature insulating cover (Gatorade Skins™) either placed in direct sunlight or shade was also monitored during the race (for 210 min). Plastic jugs (5 l) of pre-mixed sports drink (Gatorade™) and cola were cooled in ice at aid stations prior to dispensing (750 ml bottles for cycle and 200 ml cups for run course). Water was dispensed from mains or water trucks.

Results: Dry bulb temperature was 26.3 °C (19.4–29.7 °C) with an average relative humidity of 68 ± 8.8%. Radiant temperature, calculated from black globe, was on average 38.6 ± 7.0 °C and reached a maximum of 41.5 °C. WBGT was 25.2 ± 2.4 °C (range 20.5–28.1 °C) was within the increased risk category for heat illnesses. On the cycle course, competitors received water at 16 ± 6.9 °C between 0800 and 1000 h however this rose to 25.6 ± 2.5 °C between 1200 and 1300 h. A similar trend was observed with sports drink temperatures, commencing at 20.1 ± 3.7 °C and rising to 26 ± 3.3 °C. Discarded fluid in bottles on the cycle course was 28.0 ± 3.2 °C. Water on the run course was warmer (26.3 ± 2.3 °C) compared to the cycle; sports drink and cola were similar (25.2 ± 1.8 °C and 24.7 ± 4.4 °C, respectively). Higher beverage temperatures on the run compared to the cycling course are likely the result of a smaller thermal mass (178.2 ± 74.8 g vs. 477.5 ± 111.3 g) and higher radiant temperature (39.9 ± 6.3 °C vs. 38.1 ± 7.8 °C). Gatorade Skins™ significantly reduced the rate of temperature rise compared to a naked bottle in both the sun (6.4 ± 1.4 °C h−1 vs. 7.1 ± 1.9 °C h−1 respectively, p < 0.01) and the shade (4.6 ± 1.1 °C h−1 vs. 4.7 ± 0.9 °C h−1, respectively, p < 0.001). Beverages remained palatable (<20 °C) longer with the skin than without (sun: 45 ± 23 min vs. 20 ± 8 min, p < 0.05; shade: 110 ± 37 min vs. 50 ± 26 min p < 0.001).

Conclusion: Beverage temperature was influenced by environmental conditions and aid station cooling practices. Strategies including shade to reduce radiant heat, adequate ice cooling and insulated drink holders for beverages help to reduce the rise in beverage temperature to unpalatable ranges.

Abstract only.