Self-paced exercise performance in the heat after pre-exercise cold-fluid ingestion

Area of Science:

• Exercise Physiology
• Environmental Heat Stress
• Thermoregulation

Background:

• Precooling, or reducing body temperature before exercise, enhances physiological function and performance in hot environments.
• A practical precooling method for use at athletic venues has been lacking.

Purpose of the Study:

• To verify if ingesting cold fluid before exercise, without during-exercise fluid intake, lowers core temperature.
• To assess if this cold fluid ingestion improves exercise performance in heat.

Main Methods:

• A randomized controlled trial was conducted in a controlled environmental chamber (32°C, 60% humidity).
• Seven male cyclists ingested 900 mL of cold (2°C) or control (37°C) water before exercise.
• Key outcomes included rectal temperature, thermal comfort, cycling distance, and power output.

Main Results:

• Cold fluid ingestion significantly reduced rectal temperature during rest and early exercise compared to control.
• Cyclists ingested cold fluid covered greater distances and achieved higher mean power output.
• No significant differences were found in pacing, skin temperature, heart rate, lactate, comfort, exertion, or sweat loss.

Conclusions:

• Pre-exercise ingestion of cold fluid is a simple and effective precooling strategy.
• This method is practical for field-based application at athletic venues.