Ad libitum ice slurry ingestion and half-marathon performance in a hot environment: A study comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 C

Ice slurry ingestion during prolonged exercises may improve performance in hot environments; however, the ideal amount and timing of ingestion are still uncertain. We determined whether ad libitum ice slurry ingestion influences physiological and perceptual variables and half -marathon performance while comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 C-degrees. Ten trained participants (28 +/- 2 years; mean and SD) were required to run two half marathons while consuming either ice slurry (-1 C-degrees; Ad -1) or water (37 C-degrees; 37 CE) ad libitum. They then performed two other half marathons where, during one, they were required to ingest an amount of water equivalent to the amount consumed during the Ad -1 trial (Pro37), and in the other, to ingest ice slurry in the amount consumed during the 37 CE trial (Pro -1). During the half marathons, dry-bulb temperature and relative humidity were controlled at 33.1 +/- 0.3 C-degrees and 60 +/- 3%, respectively. Ad -1 ingestion (349.6 +/- 58.5 g) was 45% less than 37 CE ingestion (635.5 +/- 135.8 g). Physical performance, heart rate, perceived exertion, body temperatures, and thermal perception were not influenced by the temperature or amount of beverage ingestion. However, a secondary analysis suggested that lower beverage ingestion was associated with improved performance (Ad -1 + Pro37 vs. 37 CE + Pro -1: -4.0 min, Cohen's d = 0.39), with a significant relationship between lower beverage ingestion and faster running time (b = 0.02, t = 4.01, p < 0.001). In conclusion, ice slurry ingestion does not affect performance or physiological or perceptual variables during a half marathon in a hot environment. Preliminary evidence suggests that lower beverage ingestion (ice slurry or warm water) is associated with improved performance compared to higher ingestion.