Every summer, public transport, and particularly the metro, becomes the scene of memorable heatstrokes. While the thermometer sometimes displays a terrible 41°C on the platforms or in the trains, our body is subjected to a severe test. In just 20 minutes, a cascade of physiological reactions is triggered to prevent us from overheating.
Thermoregulation: how the body reacts to overheating
Faced with an ambient temperature of 41°C, the human body does not remain passive. It immediately activates its cooling systems to maintain its internal temperature around 37°C.
“In 20 minutes at 41°C, your body activates defenses to cool itself, but they are quickly used: you sweat a lot, the skin turns red, you may feel tight, tired or have a headache. explains Dr. Gérald Kierzek, emergency physician and medical director of True Medical.
This mechanism is based on two main actions:
- Vasodilation: The body circulates more blood to the skin to dissipate heat, which explains the red coloring of the face;
- Sweating: The activation of perspiration helps cool the skin through the evaporation of sweat.
However, this system has its limits. Dr. Kierzek recalls that “sweating a lot uses up water and salt reserves; the heart therefore beats faster to compensate. In addition, the metro environment plays a major role: “If the air is humid, sweat doesn’t evaporate well and you don’t cool down effectively.”
Fatigue, headaches: symptoms that are easy to spot
When the machine races in a crowded train, several physical signals should alert you. They reflect the body’s struggle against this stifling atmosphere.
The first signs appear quickly on the skin and in general: profuse sweating, red skin, as well as an intense feeling of heat and tightness.
And if exposure continues during the journey, other symptoms appear, notably a feeling of pronounced thirst and great fatigue, but also headaches, dizziness or nausea. “Muscle cramps may occur in some passengers, more frequently after physical exertion, such as running to catch the subway.“.
From a simple slack to emergency: when does it become dangerous?
There is a clear line between heat discomfort and actual endangerment to the individual’s life. You need to know how to make the distinction in order to react in time.
Before reaching the critical stage, the body goes through a phase of heat exhaustion and dehydration. This situation is particularly delicate for people already suffering from chronic pathologies: it can in fact aggravate a fragile heart, diabetes, or a respiratory disease.
The tipping point toward medical emergency, called “heat stroke,” is recognized by severe neurological and behavioral signs.
According to the medical director of True Medical, “If the person becomes confused, very drowsy, has seizures, loses consciousness, or their temperature seems very high, it is an emergency.”
Good reflexes to protect yourself immediately
Can we really stay at 41°C without risk? The answer is complex. As Dr. Gérald Kierzek points out, “There is no single ‘safe’ duration: it depends on humidity, sun, effort, age and state of health. One certainty remains:Going a long time without drinking or cooling down quickly increases the risks.”
To get through these heat waves safely, here are some simple tips to apply right away:
- Take shelter: Look for a cool or shaded place as soon as you get out of the train and reduce physical activity;
- Hydrate wisely:
Drink water or lightly sweetened drinks regularly, but definitely avoid alcohol and very sugary drinks which promote dehydration; - Cool down: Remove unnecessary layers of clothing, refresh the skin with water or a damp cloth, and ventilate if possible;
- Be supportive: Monitor children, the elderly and the sick, who are constitutionally the most vulnerable.
The emergency reflex: “If the person shows confusion, severe vomiting, loss of consciousness or stops sweating with hyperthermia, call for help and start cooling them.”insists Dr. Kierzek.
In summary, a temperature of 41°C in the metro is never harmless for the body, which must draw on its reserves from the first twenty minutes to maintain its balance. At the slightest doubt or when faced with confused behavior by a third party, the reflex must remain the same: alert emergency services without delay.