REF-968 · Rinaldi et al., 2023 · Biology of Sport, Vol. · Paper · PubMed

One hour of internal precooling with cold water/menthol enhances cycling performance in a heat/wet stress environment: A pilot study

Blimited evidenceMeasured on trained to highly trained athletesWritten before October 2026, being re-checked

The study compared how long to precool before aerobic exercise under heat/wet stress. Seven trained, heat-acclimated male cyclists rode 1-hour time trials in hot, humid conditions.

Beforehand they drank either (1) a neutral 23°C drink during the whole 1-hour pre-exercise rest (Neutral), (2) a -1°C ice-slush/menthol drink in just the final 30 min of that rest (Pre-30), or (3) the same -1°C ice-slush/menthol drink for the whole 1-hour rest (Pre-60). Cold water/menthol at 3°C was drunk during exercise in all conditions.

Pre-60 produced significantly better performance than Pre-30 or Neutral, which did not differ from each other. Rectal temperature during the rest period was significantly lower with Pre-60 than with Pre-30 or Neutral.

Participants

n=7 heat-acclimated and trained male cyclists. Age and fitness values are not given in the abstract.

Protocol

1-hour cycling time trials in a hot and humid environment (temperature and humidity are not given in the abstract).
Three conditions in the 1-hour rest before exercise: Neutral (a 23°C neutral drink across the hour), Pre-30 (a -1°C ice-slush/menthol drink in the final 30 min only), Pre-60 (the -1°C ice-slush/menthol drink for the full hour).
In each condition: cold water/menthol at 3°C during the exercise.
Measures: performance, rectal temperature, thermal comfort, thermal sensation, rating of perceived exertion.

Key Results

Pre-60 beat both Pre-30 and Neutral on performance, significantly (p=0.003; F(2,12)=9.50, ηp2=0.61 for the condition effect); Pre-30 and Neutral did not differ.
Rectal temperature at rest was significantly lower with Pre-60 than with Pre-30 or Neutral (p=0.035; F(2,12)=4.48, ηp2=0.43 for the condition effect).
Condition had no effect on thermal comfort or on rating of perceived exertion.
Pre-60 had a positive effect on thermal sensation at rest (Friedman condition effect: p=0.035 at 40 minutes and p=0.018 at 45; p=0.086 at 60 minutes) and in exercise (p=0.037 at 5 minutes, p=0.039 at 60).
The abstract gives no distances, power values or percentage differences.

Practical Application

In seven heat-acclimated, trained male cyclists (crossover pilot), drinking an ice-slush/menthol beverage at -1°C through the whole hour before a 1-hour time trial in humid heat gave a better performance than drinking it for only the last 30 min or drinking a neutral beverage (p=0.003), and lowered rectal temperature during the rest period; 30 min of precooling was no better than the neutral drink. To "how long before a hot race should I start on the ice slush?": in this pilot the full hour worked and the last half hour alone did not.
All three conditions included cold water/menthol during the ride, so the result is about the precooling hour added on top of that; the authors describe a cumulative effect.
The precooling drink was both ice-cold and mentholated, and the control was neutral and without menthol in the rest period: the trial cannot say how much of the effect is the cold and how much the menthol.
Do not quote a distance or a percentage gain from this entry; the abstract reports none.
Not from this paper: menthol and drink temperature were separated in REF-967 (both helped); ice-slurry and other precooling evidence is in REF-111 and REF-112; the base's protocol is in SYNTH-25.

Limitations

A pilot with n=7, men only, all heat-acclimated; randomisation and blinding not stated in the abstract.
Cold and menthol are confounded in the precooling drink.
No effect size in units of performance, and no ambient temperature or humidity, in the abstract.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

crossover pilot, n=7; randomisation and blinding are not stated in the abstract