Caffeinated Ice Slushy Enhances 1,200 kJ Cycle Time-Trial Performance in the Heat.

Area of Science:

• Exercise Physiology
• Sports Nutrition
• Environmental Extremes

Background:

• Athletes often face performance decrements in hot and humid conditions.
• Precooling strategies, such as ingesting ice slushies, can mitigate heat stress.
• Caffeine is a known ergogenic aid that may enhance endurance performance.

Purpose of the Study:

• To investigate the impact of caffeine combined with a carbohydrate ice slushy on cycling time-trial (CTT) performance in heat.
• To compare the effects of a carbohydrate-only ice slushy versus a caffeine-and-carbohydrate ice slushy on physiological and performance outcomes.

Main Methods:

• Nine male cyclists/triathletes participated in a single-blind, counterbalanced study.
• Participants ingested either a carbohydrate-only (CON) or a carbohydrate-caffeine (CAF) ice slushy (6.8 g/kg ice, 6% carbohydrate, 3 mg/kg caffeine for CAF) over 30 minutes prior to exercise.
• A 1,200 kJ cycling time-trial was performed in a controlled hot and humid environment (33 °C, 60% RH).

Main Results:

• The caffeine-and-carbohydrate slushy (CAF) resulted in a significantly faster CTT completion time compared to the carbohydrate-only slushy (CON).
• Faster split times were observed in the CAF condition from 800 kJ to 1,200 kJ of the CTT.
• Both conditions similarly reduced rectal temperature, with no significant differences in heart rate, blood lactate, perceived exertion, or thermal sensation between CAF and CON.

Conclusions:

• Precooling with a carbohydrate ice slushy containing caffeine enhances cycling time-trial performance in hot conditions.
• The addition of caffeine to a carbohydrate-based ice slushy provides performance benefits beyond carbohydrate alone for endurance athletes in the heat.
• Caffeine-fortified ice slushies represent a viable ergogenic aid for athletes competing in warm environments.