Heatstroke Prevention During Exercise | Prevention Methods, Cancellation Criteria, and First Aid in Sports

Why does the risk of heatstroke increase during exercise? An explanation of how body temperature rises.

During exercise, a large amount of heat is generated in the muscles, causing body temperature to rise.
The body sweats, and uses the heat of vaporization produced when that sweat evaporates to regulate body temperature.
However, in environments with high temperatures and humidity, sweat does not evaporate easily, causing heat to build up inside the body.

If this condition persists, the body's temperature regulation system will not function properly, leading to heatstroke, which causes symptoms such as dizziness, headaches, and nausea.

Five basic measures you can implement right now to prevent heatstroke during exercise.

Heatstroke can be prevented by having the right knowledge and taking precautions.
When exercising, it is important to thoroughly implement basic measures such as staying hydrated, dressing appropriately, and acclimatizing to the heat.
Here are five basic measures that anyone can implement immediately.

Solution 1: Before you get thirsty! The correct timing and amount of hydration and salt intake during exercise.

By the time you feel thirsty, your body is already dehydrated.
To prevent heatstroke, it's important to replenish fluids frequently, even before you feel thirsty.
A good guideline is to drink about one glass of water before, during, and after exercise.

When you sweat, you lose not only water but also salt, so in addition to water and tea, use sports drinks or oral rehydration solutions that contain salt and sugar to replenish the lost components.

Countermeasure 2: How to proceed with "heat acclimatization" training to get your body used to the heat before the peak of summer.

Heat acclimatization is the process of the body becoming accustomed to heat.
Before the heatwave sets in, start with light exercise such as walking in a slightly warm environment, and gradually increase the duration and intensity of your exercise over a few days to two weeks. This will help your body adapt to the heat.
If you're hesitant about exercising outdoors, we recommend going to a sports club where you can work up a good sweat in a cool environment.
Choosing a sports club that offers access to hot springs and saunas after training makes it possible to gradually acclimatize to the heat indoors without putting undue strain on yourself.
As you become acclimatized to the heat, your ability to sweat improves, making it harder for your body temperature to rise, and thus you become less susceptible to heatstroke.

Solution 3: Choose moisture-wicking and quick-drying clothing! Key points for clothing that releases heat.

The clothing you wear during exercise greatly affects your ability to regulate your body temperature.
Choose clothing made from materials with excellent moisture-wicking and quick-drying properties, which allow sweat to dry quickly and heat to escape efficiently.

Loose-fitting clothing allows for better ventilation and prevents heat buildup compared to clothing that clings to the body.
Additionally, wearing a hat and sunglasses is effective in avoiding direct sunlight when outdoors.

Countermeasure 4: Choose cooler times of day and take frequent breaks to prevent your body temperature from rising.

Exercising in direct sunlight significantly increases the risk of heatstroke.
You should especially avoid the time between 10 AM and 2 PM when the sun is strong and temperatures are high.
When exercising, choose the relatively cooler times of day, such as early morning or evening.
If your schedule requires you to exercise during the day, try to exercise indoors in a way that is comfortable for you, such as by using an air-conditioned sports club.

Additionally, during exercise, avoid overexertion, take regular breaks every 30 minutes or so, and rest in the shade to prevent your body temperature from rising excessively.

Countermeasure 5: Sleep deprivation and hangovers are dangerous! Checklist of physical condition before exercise

Poor physical condition such as lack of sleep, fatigue, hangovers, or feeling under the weather can impair the body's regulatory functions and increase the risk of heatstroke.
Before exercising, always check your physical condition, and if you have any concerns, it is important to stop or postpone your exercise rather than pushing yourself too hard.
Especially after exercise, fatigue tends to accumulate, so be sure to get enough rest and nutrition.

Knowing when to stop is also important! Criteria for deciding when to stop exercising using the WBGT (Wet Bulb Globe Temperature) index.

The WBGT (Wet Bulb Globe Temperature) is an index used to objectively assess the risk of heatstroke, taking into account not only temperature but also humidity and solar radiation.
Instead of relying solely on individual perception, you can use WBGT values ​​as a reference to determine whether the environment is safe for exercise.
Especially when engaging in strenuous exercise, it is essential to check the WBGT (Wet Bulb Globe Temperature) and, if the conditions are dangerous, to change your plans or have the courage to stop.

[Danger Level] Exercise should be stopped if WBGT is 31℃ or higher.

When the WBGT (Wet Bulb Globe Temperature) reaches 31°C or higher, it is considered a "dangerous" level, indicating an extremely high risk of heatstroke.
In these conditions, everyone is at risk of heatstroke, regardless of age or physical condition.

Guidelines from organizations such as the Japan Sports Association also state that exercise should be avoided in principle when the WBGT (Wet Bulb Globe Temperature) is 31°C or higher, and exercise should be avoided except in special circumstances.

[Severe Warning Level] When the WBGT is between 28 and 31°C, avoid strenuous exercise and take frequent breaks.

A WBGT (Wet Bulb Globe Temperature) of 28°C to less than 31°C is considered a "severe caution" level.
At this level, the risk of heatstroke increases, so prolonged, strenuous exercise should be avoided.
When exercising, it is necessary to take longer and more frequent breaks than usual, and to actively replenish fluids and electrolytes.

Be sensitive to any changes in your physical condition, and stop exercising immediately if you feel even the slightest abnormality.

Where can I check the WBGT (Wet Bulb Globe Temperature) index? Use the Ministry of the Environment's website or app.

You can check the WBGT (Wet Bulb Globe Temperature) for various locations across Japan on the Ministry of the Environment's "Heatstroke Prevention Information Website," where you can find both predicted and actual values.
This site provides hourly figures and detailed explanations, and is free for anyone to use.

Additionally, some private weather information websites and smartphone apps provide WBGT data, so make it a habit to easily check it before exercising.

Suspecting heatstroke in yourself or a friend? Here's how to perform first aid on the spot.

If you experience symptoms suggestive of heatstroke, such as dizziness, headache, or nausea during exercise, prompt and appropriate first aid is key to recovery.
Knowing the correct procedures can help protect your own safety and the safety of those around you.
Here, we will explain the basic steps for first aid that can be performed on the spot.

STEP 1: First, take refuge in a cool place such as a shady spot or an air-conditioned room.

If you suspect someone is suffering from heatstroke, the first thing you should do is quickly move them away from direct sunlight and hot, humid environments.
Move it to a cool place, such as a shady or well-ventilated area, or ideally, an air-conditioned room or car.
Moving them to a safe place is the first step in lowering their body temperature.

STEP 2: Loosen your clothing and focus on cooling areas where large blood vessels are located.

Once you move to a cooler place, loosen your belt, tie, and shirt buttons to allow heat to escape from your body more easily.
Next, to efficiently lower body temperature, we cool areas where large blood vessels run close to the surface of the body.
Apply concentrated cooling to areas such as both sides of the neck, armpits, and groin using ice packs, wet towels, or chilled plastic bottles.

STEP 3: If the person is conscious, give them oral rehydration solution or a sports drink.

After confirming that the person is fully conscious and not experiencing nausea, administer fluids and electrolytes.
In this situation, oral rehydration solutions or sports drinks that contain a balanced amount of salt and sugar, in addition to water, are suitable.
If the person is able to drink on their own, give them small amounts frequently.

STEP 4: If the animal does not respond to calls or is unable to drink water on its own, immediately call 119 (emergency services).

If your pet is unresponsive to calls, appears disoriented, or is unable to drink water on its own, it may be suffering from severe heatstroke.
In situations like this, do not hesitate to call 119 immediately, and continue to cool the body while waiting for the ambulance to arrive.
On-the-spot decisions can save lives.

Frequently Asked Questions about Heatstroke Prevention During Exercise

Here, we will answer some of the most common questions people have regarding heatstroke prevention during exercise.

Q1. Which is best to drink during exercise: water, tea, or sports drink?

During prolonged exercise or heavy sweating, you lose not only water but also salt and minerals, so sports drinks or oral rehydration solutions that can replenish these are suitable.
Especially during activities like running, drinking large amounts of water alone can disrupt the body's electrolyte balance.
The caffeine in tea has a diuretic effect and is therefore not recommended from a hydration standpoint.

Q2. Are heatstroke prevention measures necessary even when exercising indoors?

Yes, it is necessary.
While indoor spaces such as gymnasiums and fitness centers are often perceived as safer than the outdoors, poor ventilation and high temperatures and humidity increase the risk of heatstroke.

Just like outdoors, it's important to stay hydrated indoors and to use air conditioners or fans to properly manage room temperature and humidity.

Q3. What are some points that adults should pay particular attention to when children are playing sports?

Children are more susceptible to heatstroke than adults because their thermoregulatory functions are less developed.
Additionally, they may have difficulty communicating thirst or feeling unwell.

Adults around the child, such as coaches and parents, need to pay close attention to the child's complexion and how much they are sweating, and take extra care by scheduling hydration and rest breaks at set times.

Summary

Heatstroke during exercise can be prevented by understanding how body temperature rises and taking appropriate preventive measures.
Before exercising, check your physical condition, and during exercise, be sure to replenish fluids and electrolytes before you get thirsty, wear moisture-wicking and quick-drying clothing, and take frequent breaks.
Furthermore, it is necessary to objectively judge whether or not exercise is appropriate by referring to the WBGT (Wet Bulb Globe Temperature) index, and to have the courage to stop if the situation is dangerous.
It is important to fully understand that exercising outdoors in the summer increases the risk of heatstroke, and to exercise in a cool, air-conditioned environment.

If you experience symptoms that suggest heatstroke, take immediate first aid measures such as moving to a cool place, cooling your body, and rehydrating.