Effect of Ingestion of Ice Slurry on the Sleep Quality of Rugby Union Players in the Summer Season

The aim of this study was to investigate the effect of ingestion of ice slurry before bedtime on the sleep quality of rugby union players in the summer season. Thirteen healthy male university rugby union players volunteered for this study. The participants ingested either ice slurry or a room-temperature beverage (control) 30 min before bedtime. A wearable activity-based sleep monitor was used to analyze objective sleep parameters, and the subjective sleep scores were assessed using the Oguri–Shirakawa–Azumi Sleep Inventory, middle-aged and aged version (OSA-MA). No differences in the amount or efficiency of sleep were observed between the ice slurry/control beverage conditions. Significant shortening of the sleep latency was observed in the ice slurry condition as compared with the control beverage condition. Moreover, significant improvement of the subjective sleep score for “feeling refreshed” on the OSA-MA was observed in the ice slurry condition. There were no significant differences in the other subjective sleep scores between the two conditions. The results suggest that ice slurry ingestion before bedtime may improve the latency of sleep onset, accelerate recovery from fatigue, and be useful as a sleep improvement strategy in rugby union players engaging in exercises during the summer season.