perform at your best in the summer heat with Pre-Cooling

6 min read

Updated: 23 February 2026

Something that undoubtedly lowers athletes' performance, regardless of the sport, is heat, which we have previously discussed. When the temperature starts creeping above 18 degrees, many of us feel extra tired. If you're competing during the summer months, Pre-Cooling, meaning lowering your body's temperature before starting, can be a remarkably simple and effective trick to increase your margin until the level where high body temperature starts affecting performance. The main question is when pre-cooling works best, how significant the effect usually is, and which methods are most practical. The conclusion is that pre-cooling generally helps more as it gets warmer and the more intense your effort, with simple solutions like cold drinks or slushes often being both effective and practical. So now let's dive in!

Background

We reviewed two articles from 2012: a Meta-Analysis from Germany (27 studies, totaling 269 participants) and a systematic review from England (13 studies).

We emphasize the meta-analysis as it included “performance” as a criterion. Participants were endurance athletes primarily involved in running, cycling, and triathlon. The studies used a cross-over design, meaning each participant served as their own control; all studies were independently reviewed.

The participants were split into two groups: those with 55–65 ml/kg/min oxygen uptake and those above 65 ml/kg/min. All were well-trained to very well-trained, but none were official professionals or elite athletes (such participants were excluded). Now you know who was studied and whether the results apply to you.

Why Heat Lowers Performance

Our reduced performance in heat is due to several factors. On one hand, local effects like altered fluid volumes and reduced blood flow. On the other hand, enzymes that regulate energy metabolism are heat-sensitive and function less efficiently at higher temperatures.

Perhaps most importantly is central fatigue: our central nervous system is affected early on in the heat. Studies indicate that the brain slows down signals to the muscles so they can't work as hard, for example at 40 degrees compared to 18 degrees. If researchers electrically stimulate the muscles, they can contract more forcefully — demonstrating that the local capacity exists, but the brain sets the limit sooner.

How Pre-Cooling Works

Pre-Cooling involves using external aids to lower the body's core temperature before starting, giving the athlete more leeway before overheating hampers performance. By starting cooler, you can store more heat (what research calls "heat storage capacity") before the body reaches dangerous levels – allowing you to maintain high intensity longer and perform better.

In two studies in the review, participants reached a higher body temperature at exhaustion after Pre-Cooling compared to the control groups. Researchers suggest this might be because athletes could generate more heat since they performed better. The allowed increase in intensity (and therefore performance) might be due to either the brain being cooled and not putting a stop, or the afferent (sensory) nerve pathways sending signals that the body is still cool, like "Hey brain, it’s cool down here, keep pushing".

A little side note: nerve signals travel from the body's local areas via the spinal cord up to the brain. There are stories of pro cyclists using ice-filled mesh socks along the spine to influence thermal signals before they ascend to the brain. Elite athletes are, as you know, inventive 😉.

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When Pre-cooling Provides the Best Results

In the meta-analysis, 18 studies were conducted at temperatures above +26 degrees, while 8 were conducted at 18–26 degrees. One study did not specify the outdoor temperature. The basic rule is simple: the effect of Pre-Cooling increases as the outdoor temperature rises.

What impact can you expect?

The performance increase across all studies in the meta-analysis averaged +4.9%. Various types of tests were used:

  • Highest effect (+8.6%) in open-ended tests (continue until exhaustion at a given speed).
  • In time trials and incremental tests (e.g., maximal oxygen uptake – VO2max – to exhaustion), the increase was 4.4–6.0%.

The benefit of Pre-Cooling also depends on how much heat you generate yourself. If you walk calmly, you won't see any effect. But if you push yourself hard — and can produce a lot of energy and thus heat — there's a lot to gain. The highest effect was seen in individuals with a VO2max over 65 ml/kg/min: on average, 7.7% better. Those with 55–65 ml/kg/min performed on average 3.8% better. Interestingly, this is the opposite of many other interventions where recreational athletes often gain the most; here, it's advantageous to be really well-trained, as you can generate more heat and thus benefit more from starting cold.

Temperature and Duration

At temperatures above 26 degrees: +6.6%. At temperatures between 18–26 degrees: +1.4%. The effect over time generally follows an inverted U-curve. You gain the most advantage during shorter events (e.g., 5,000 m, 10,000 m) when intensity is high. As time progresses, this effect decreases. After about 60 minutes, the benefits of pre-cooling usually fade—likely because the initial advantage has been expended. If you maintain cooling during the activity, the effect can naturally continue, but if you only consider pre-cooling before starting, the effect seems to last just over an hour.

Which method works best in practice?

Which cooling method is best? There are many ways to cool down before a start: cold shower, cold bath, ice packs, cooling vest, standing in a cold room, or drinking ice-cold fluids (slushy). The meta-analysis shows the following performance increases with different methods: Ice-cold drink: +15% Cold room: +10.7% Ice packs: +5.6% Cooling vest: +4.8% Cold shower: +1.2% In practice, one method doesn’t need to exclude another, but in studies, one method is often compared at a time. Feel free to go all out — go crazy bananas — but in the field, it's often best to choose what's most practical. The systematic review deemed "cold water immersion" as the most effective, while the meta-analysis showed ice-cold drink as the most effective. 

Slush/ice-cold drink as a "field solution"

Both recommend an ice slushy at around −1 to 0 degrees as the most practical option. Consume this drink 15–45 minutes before starting, over 5–15 minutes. A smart tip is to combine your warm-up with drinking ice: freeze your sports drink (e.g., U Sport) to get the last 50 g of carbohydrates in before you start. You'll hydrate and slightly lower your core temperature—a game-changer on a hot day. Remember, the goal is to reduce your core temperature by about 1–1.5 degrees, not just the local muscle temperature, so be cautious with extreme ice baths that cool your muscles too much. Transport an icy drink easily in a cooler with ice or cold packs. Prepare the day before; if you have a slushy machine at home (which costs 300–700 SEK), you're set. Crushed ice also works. If you're on the go, most grocery stores have crushed ice, and yes, you can always stop by a fast-food chain to buy their ice.

Update and New Research

A recent study from February 2018 shows that pre-cooling with ice, where participants consumed 7 g of ice per kilo of body weight (i.e., about 500 g for a 70 kg person), was as effective as heat acclimatization in terms of subsequent performance in 35-degree heat with 50% humidity. This provides us with a much more time-efficient and economical method for "heat acclimatization" before shorter distances, like intervals and threshold sessions.