How to perform in the heat

Before getting to the heart of the matter, it is important to understand what happens in our bodies in extreme heat.

Thermoregulation

Under normal circumstances, physical activity alone generates a significant amount of heat, which raises our internal temperature. At the same time, our metabolism works hard to regulate everything, in addition to supporting muscle contraction. Depending on the relative humidity, ambient heat, type of clothing, and intensity of the effort, our body will try to fine-tune itself to prevent excessive heat buildup by increasing the vasodilation of our blood vessels and producing a fair amount of sweat. Much like a radiator, our body cools us down at the surface of our skin and creates exchanges between its internal temperature and the ambient air. 

When the body is no longer able to regulate heat exchange properly, it can potentially enter a state of heat stress, causing discomfort that can affect our performance.

Collateral damage

Gastrointestinal disorders

Digestive discomfort is a constant threat to endurance athletes—and haunts many of them. It can be caused by poor nutrition management before exercise, excessive carbohydrate intake during activity, or increased transit time due to the constant intensity imposed. It is often this discomfort that impairs performance. Endurance training in hot conditions also causes intestinal function to be disrupted. This is partly because blood flow is directed to the muscles and peripheral circulation (thermoregulation), resulting in reduced blood flow to the intestines. Depending on the duration and intensity, an inflammatory response may also occur, which will impair both digestion and nutrient absorption.

Aerobic performance

Eventually, the effect of heat on various biological parameters—such as increased body temperature—will have a greater or lesser impact on an athlete's performance. This imposed stress alters aerobic metabolism, which will then quickly use up glycogen reserves. In other words, it is as if our body becomes more energy-intensive and we open the tap that lets energy pass through in the form of sugar, which is well stored, to the maximum. Maximum high-intensity efforts will then be much more difficult to sustain.

Fight fire with fire

An effective way to prepare yourself to tolerate heat while still performing at your best is to train as much as possible in these conditions. This is known as acclimatization. The more your body gets used to training in the heat, the better it will adapt to this environment that is hostile to your performance. For example, it will adjust by increasing blood volume, reducing heart rate (to prevent overheating), and improving electrolyte balance and exchanges in the body. A well-acclimatized athlete will potentially sweat more than normal, but the amount of sodium excreted will be lower.

To fine-tune your acclimatization, there are not 36 solutions: you have to keep an eye on the weather forecast and try to "take advantage" of hot days. 

The key: stay well hydrated

To minimize the discomfort caused by heat, it is important not to underestimate hydration, and above all to plan how to rehydrate before, during, and after exercise. First, you need to know yourself well and try to find out whether, genetically, you lose a lot of sodium during exercise or not. There are significant differences between individuals: some will lose only 50 mg/h, while others will lose around 300 mg/h. A good way to find out is to examine your clothes after exercising in the heat. Some will have whitish rings (a sign of sodium loss), while others will simply be soaked.

The more sodium you lose, the more important it is to add electrolytes to your water to rehydrate properly without further diluting the amount of electrolytes in your body. Conversely, someone who sweats profusely but does not lose much sodium will need to adjust the amount of electrolytes added to their bidons accordingly, making sure to drink continuously to maintain a good fluid volume.

Finding your strategy

BEFORE (2-3 hours)	DURING	AFTER
Drink enough to stay well hydrated, and a little more depending on the effort ahead (cold water + electrolyte solution). Eat a filling meal (protein, carbohydrates, fiber) that you will have time to digest.   Add menthol via a cold drink or apply directly to the skin in gel or spray form to cool down (*commercial solutions recommended*).	Drink enough every 15-20 minutes (drink with electrolytes + carbohydrates). Add ice cubes to try to keep the drink below 20 degrees. Stop during the race to refill your bidons an ice-cold drink.	Drink enough fluids within 2 to 4 hours after exercise. Gradually add salty foods (salted nuts, pretzels, pasta salad with feta cheese, etc.) to rehydrate more effectively. Check the color of your urine to gauge your hydration level and adjust your water intake for the rest of the day/evening as needed.

 

To each his own

Obviously, when trying to understand each person's response to training, we must take into account the variations between all athletes. There are as many ways to adapt to training as there are individuals. The best way to effectively play with the many performance parameters is to know yourself well and, above all, to do several tests during training. It may be useful to keep a journal containing this type of data to compare one element at a time and its impact on your performance. At the same time, it is also important to find a consistent and realistic strategy that fits your lifestyle if you want it to be sustainable.

Although certain parameters can always be modified to optimize environmental variables, we must not neglect training in its simplest form, but above all the very essence of sport, which is to enjoy pushing ourselves beyond our limits, regardless of the conditions. When morale is high, we thirst for adventure!