Running in high temperatures puts a strain on the heart, torn between pumping blood to the muscles to make them move or sending it to the skin to cool you down. Learning to apply the practical pre-cooling technique allows you to lower your heart rate and prolong performance, delaying the moment when fatigue takes over.
- In the heat, the heart works twice as hard to cool the skin and nourish the muscles.
- “Pre-cooling” consists of lowering your core temperature before lacing up your shoes.
- Drinking very cold liquids and wetting your wrists and neck tricks the body’s thermodynamics.
- Starting slow helps the body get used to the thermal shift without immediately running out of breath.
- Listening to warning signs, like chills under the sun, is vital to stop in time.
When temperatures start to rise in late May, your usual runs become exhausting. Your legs feel heavy, your breath is short, and the stopwatch shows much slower times than usual. You haven’t lost your fitness in a week: it’s just physics presenting the bill. The body struggles tremendously to manage effort under the sun. Yet, there is a trick widely used by professionals, called “pre-cooling”, that you can apply at home to fool the thermometer and enjoy your run without feeling like a boiling engine.
The Thermodynamics Challenge: Cardiac Effort Under the Sun
Imagine your body as an engine. When you run, you produce heat. To avoid melting down, the system sends large amounts of blood to the skin to make you sweat. The sweat evaporates and cools you down.
The problem is that the blood going to the skin is taken away from the muscles, which desperately need it for oxygen and energy. Your heart, caught in the middle of this war, starts beating much faster to try and please everyone. That’s why, at the same speed, your heart rate is much higher in the summer than in the winter. It’s pure survival.
The Concept of Pre-Cooling: Delaying Overheating Time
Since we can’t turn off the sun, we can, however, delay the moment when our “engine” boils over. The principle of pre-cooling is very simple: if you lower your core temperature before you start running, it will take the body much longer to reach the critical alarm level.
It’s like putting ice in a cooler before putting the drinks in. By starting from a slightly lower core temperature than normal, you give your body precious minutes of comfortable running before the heart has to start working overtime to cool you down.
Practical Methods Before Heading Out: Cold Liquids and Targeted Showers
To lower your core temperature, you don’t need to lock yourself in a freezer. There are two practical methods to do at home in the twenty minutes before heading out.
The first goes through the stomach: drink a nice bottle of cold water (not freezing cold so as to give you a stomachache, but very cold). Crushed ice drinks (“slushies”) are also often used, as they absorb a lot of internal heat to melt.
The second method is to wet the points where veins pass very close to the skin with cold water or ice: the wrists, the neck, and the groin area. By cooling the blood in these points, you circulate cool liquid throughout the body as if it were a natural air conditioning system.
Pace Management in the First Kilometers of Thermal Transition
Leaving the house nice and cool and immediately sprinting like a coiled spring is a mistake. The external wall of heat is still there waiting for you. If you start too fast, you cancel out the effect of pre-cooling in two minutes and send your nervous system into a tailspin.
The first few kilometers should serve as a transition. Start at a slower pace than your usual easy pace. Let your body understand that it’s hot and begin to open its pores to sweat gradually. Only when you feel that your breathing is steady and sweating is well underway can you try to slightly increase the pace, always listening to your body’s signals.
Physiological Warning Signs You Should Never Ignore
No matter how good you are at cooling down and managing yourself, extreme heat always wins. That’s why you need to know the warning signs. If you are running under the sun and suddenly stop sweating, you have a problem. It means you have run out of fluids and your body can no longer cool itself.
Other signs you should never ignore are goosebumps or chills, sudden nausea, or a feeling of dizziness. If you experience any of these, stop immediately in the shade, find something to drink, and walk. In short, organize your run smartly, cool down before you start, and don’t challenge nature when temperatures are out of control.