In short 💡
Your body maintains its body temperature at around 37°C thanks to a thermal regulation system controlled by the brain.
- When it is cold, the body reduces blood flow to the extremities and triggers shivering to produce heat.
- When it's hot, sweating and the opening of blood vessels remove excess heat.
But these mechanisms have their limits. When the body reaches its limit, external compensation solutions can extend your comfort zone and allow you to keep going.
Your body is a thermal machine, with its limits
-5°C. Your hands lose their dexterity in twenty minutes. In the middle of summer, a roofer exposed without protection sees his alertness drop after two hours. These are not whims: it's physiology at work.
The human body functions like a heat engine. Its internal temperature must remain constant, around 37°C, for all your vital functions to work properly. As soon as the environment pushes too hard (cold or heat), the thermoregulation system kicks in to compensate. But it has its limits.
Understanding how this works means understanding why the cold numbs your fingers, why the heat drains you, and above all, how to prolong this zone of equilibrium when conditions become difficult. At G-Heat, every piece of equipment we design, whether heating or cooling, is based on this logic: helping the body maintain its regulation, not replacing it.
The hypothalamus: your brain's thermostat
A control center that reacts in seconds
The hypothalamus is a small area of the brain, no bigger than an almond, located at the heart of the central nervous system. Its role is to control body temperature like a thermostat. It constantly receives data on the body's thermal state, compares it to a reference value (37°C), and triggers the appropriate response.
This regulatory mechanism operates in a closed loop. Even a deviation of a few tenths of a degree is enough to trigger a correction. All in a matter of seconds.
- Set point: 37°C ± 0.5°C for the core
- Reaction time: a few seconds after detection of a deviation
- Coordination: nervous system, hormones, and metabolism work together
Temperature sensors: your sentinels under the skin
To control thermoregulation, the hypothalamus needs reliable data. Thermoreceptors play this role as sensors.
Your skin contains around 250,000 cold-sensitive and 30,000 heat-sensitive receptors, distributed across the entire skin surface. These peripheral sensors send information to the brain via nerve fibers. At the same time, central sensors—in the hypothalamus itself, the spinal cord, and deep organs—measure the temperature of circulating blood.
It is the combination of these two levels of detection that allows for precise and responsive regulation.
- Cold receptors: active between 10°C and 40°C, peak sensitivity around 25°C
- Heat receptors: active between 30°C and 45°C
- Transmission: the signal reaches the brain in a few milliseconds
Central core versus periphery: the body makes choices
Your body does not heat up uniformly. Physiology distinguishes between two areas:
- The core: brain, heart, liver, kidneys. Temperature maintained at a constant level, close to 37°C. This is the priority zone.
- The periphery: skin, superficial muscles, extremities (hands, feet, nose). Its temperature varies greatly depending on external conditions—it can drop to 20°C in the fingers in cold weather.
The principle is simple: when it's cold, the body sacrifices heat from the periphery to protect the core. Your fingers freeze first because your brain and heart come first.
“Your fingers are the first to suffer from the cold because the body protects its vital organs first. Our heating devices work precisely on this peripheral area to compensate for this natural mechanism, without interfering with the regulation of the core.”
— Gwenaël Fournet, Product Expert at G-Heat
Heat production: how the body defends itself against the cold
Shivering: your emergency heating system
When your body temperature drops below its set point, the hypothalamus triggers shivering. In practical terms, your muscles contract involuntarily 10 to 20 times per second. These contractions do not produce any useful movement, but they generate heat—up to five times your resting heat production.
The problem is that this mechanism consumes a lot of energy. It quickly depletes your glycogen reserves. After a few hours of exposure to the cold, fatigue sets in and the body no longer has the fuel to shiver.
- Trigger threshold: core temperature below approximately 36°C
- Heat production: up to 5 times the basal metabolic rate
- Limit: energy reserves depleted within a few hours
Vasoconstriction: blood is withdrawn to protect the heart
Even before shivering, your body activates a first reflex: vasoconstriction. As soon as the internal temperature drops to around 36.8°C, the nervous system commands the blood vessels in the periphery to constrict.
The result: warm blood remains concentrated around the vital organs. Blood flow to the fingers, toes, and nose can drop by 90%. This is why these areas become cold, white, and lose their sensitivity first.
💡 Practical advice: vasoconstriction is a normal protective mechanism, but it leads to a loss of dexterity that can be dangerous—on a construction site, on a motorcycle, or in the mountains. Direct heat to the fingers, such as that provided by heated gloves with carbon filaments, compensates for this reduction in blood flow and maintains your mobility. Without interfering with the body's natural regulation.
Metabolism: your internal furnace revs up
The third lever of thermogenesis: the body accelerates its cellular metabolism. Under the action of hormones (noradrenaline, thyroid hormones), cells intensify their internal chemical reactions. The result: more heat is produced.
The liver, muscles, and brown adipose tissue are the main players in this heat production. This is also why diet plays a key role in coping with the cold: each metabolized nutrient releases energy in the form of heat.
- Key hormones: norepinephrine, thyroxine (T4), triiodothyronine (T3)
- Brown adipose tissue: specialized in heat production
- Possible increase: up to +40% of basal metabolism during prolonged exposure to cold
Heat dissipation: how the body cools itself
Sweating: your evaporative cooling system
Sweating is your body's most effective mechanism for cooling itself. Your 2 to 4 million sweat glands secrete a liquid that is 99% water. When this water evaporates on the surface of the skin, it absorbs thermal energy: approximately 2,400 kilojoules per liter of sweat evaporated.
In extreme heat or during intense physical activity, the body can produce up to 2 liters of sweat per hour. But beware: this system depends on the humidity of the outside air. The more humid the air, the less effective evaporation is. That's why we feel stifled in hot, humid weather.
Vasodilation: opening the floodgates to dissipate heat
Unlike vasoconstriction, vasodilation opens the peripheral blood vessels. Warm blood flows to the surface of the skin to transfer its heat to the ambient air through radiation and convection.
Skin blood flow can increase from 0.5 liters per minute at rest to 7 liters per minute in situations of thermal stress. This explains why the skin reddens during exercise or in hot weather: it is a visual representation of the flow of blood to the periphery to dissipate heat.
The four ways heat is lost: radiation, convection, conduction, and evaporation
Thermolysis occurs through four modes of heat transfer. Each plays a variable role depending on the conditions:
English
| Heat Transfer Mode | Physical Principle | Share of Heat Exchange (rest, 20°C) | Reduced Efficiency when… |
|---|---|---|---|
| Radiation | Emission of infrared waves by the body | ~60 % | Outdoor temperature close to 37°C |
| Convection | Heat transfer through air movement | ~15 % | Still or very warm air |
| Conduction | Direct contact with a cold surface | ~3 % | Insulation from clothing |
| Evaporation | Transformation of water (sweat) into vapor | ~22 % | High ambient humidity (>80%) |
As soon as the outside temperature exceeds 35°C, the first three modes become less effective. Evaporation then becomes the main cooling mechanism.
⚙️ The technology explained: our cooling clothing makes use of precisely these modes of transfer. Jade Cool technology acts as an evaporation accelerator: micro-crystals of jade embedded in the fiber capture body heat and dissipate it—much like an ice cube placed on the skin. Poly Cool technology prolongs cooling thanks to super-absorbent polymer fibers that retain water. Each approach targets a specific transfer mode depending on the context of use.
Trigger thresholds: when the body goes into defensive mode
A precise hierarchy of responses, accurate to a tenth of a degree
Thermoregulation mechanisms do not all activate at the same time. They follow a precise hierarchy, triggered by internal temperature thresholds.
| Core Body Temperature | Triggered Mechanism | Type of Response |
|---|---|---|
| < 36.8°C | Peripheral vasoconstriction | Heat conservation |
| < 36.0°C | Muscle shivering | Active heat production |
| < 35.0°C | Hypothermia — medical emergency | System failure |
| > 37.2°C | Cutaneous vasodilation | Heat dissipation |
| > 37.5°C | Active sweating | Cooling by evaporation |
| > 40.0°C | Heat stroke — medical emergency | System failure |
The first reflex when faced with cold—vasoconstriction—kicks in at 36.8°C, a difference of just 0.2°C from normal. Your body reacts well before you “feel” the cold.
Cold versus heat: two opposing strategies
When faced with cold, the body adopts a defensive posture: it concentrates heat in the center, reduces exchanges with the outside world, and activates heat production. When faced with heat, the opposite occurs: it maximizes exchanges by opening the skin's blood vessels and triggering perspiration.
Important point: the ability to adapt to heat is generally higher. With acclimatization, an individual can increase their sweat volume and lower their trigger threshold. On the other hand, thermogenesis remains limited by energy reserves. Prolonged exposure to cold therefore becomes dangerous more quickly.
When the system reaches its physiological limits
Despite its precision, human thermoregulation has absolute limits:
- Below 35°C core temperature: hypothermia. The central nervous system begins to malfunction.
- Above 40°C: heatstroke. Risk of irreversible cell damage.
Between these two extremes, balance depends on the duration of exposure, the intensity of physical activity, hydration, health status, and—crucially—the equipment worn. It is in this intermediate zone, when the body is struggling but has not yet given up, that external thermal compensation devices are most valuable.
⚠️ Point of caution: the warning signs of failure are often subtle. Numbness in the extremities, slight confusion, loss of coordination, or sudden cessation of sweating in the heat. Do not ignore them: they indicate that your regulatory system is approaching its limits. In a professional environment, these symptoms should trigger an immediate halt to activity and a move to shelter.
How to optimize your thermoregulation on a daily basis
Hydration: the fuel for your thermal regulation
Water is the main vector for your thermoregulation. It makes up 99% of sweat, transports heat via the blood, and fuels all metabolic reactions. Dehydration of just 2% of your body weight already reduces your ability to sweat and increases your heart rate.
- Drink 200 to 300 ml of water every 20 minutes when exercising, regardless of the outside temperature.
- Choose slightly mineralized water to compensate for salt loss through perspiration.
- Monitor the color of your urine: dark yellow = early signs of dehydration.
- In cold weather, maintain a regular fluid intake even if you don't feel thirsty—cold, dry air accelerates fluid loss through breathing.
Movement: your best ally against the cold
Physical activity is a direct driver of thermogenesis. Muscle contraction converts chemical energy into movement and heat: only 25% of the energy produced is used for movement. The remaining 75% is released as heat. This is why you warm up quickly when walking in cold weather.
Conversely, prolonged immobility in cold conditions accelerates cooling. Basal metabolism is not enough to compensate for the losses. For static professionals—security guards, machine operators, surveillance operators—this reality makes external heat input essential when movement is not an option.
Food: the right fuel for the right season
Every food consumed produces heat during digestion. This is dietary thermogenesis. Not all nutrients are created equal:
- Proteins: 20 to 30% of their caloric value is dissipated as heat—the best thermal efficiency.
- Carbohydrates: 5 to 10% is dissipated as heat.
- Lipids: 2 to 5% is dissipated as heat.
In cold weather, a diet rich in protein and complex carbohydrates supports heat production. In hot weather, light, water-rich meals limit the thermal load associated with digestion. Food does not replace thermoregulation — it provides the fuel to keep it working throughout the day.
"In the field, users who combine hydration, appropriate nutrition, and high-performance thermal equipment significantly extend their activity capacity. Technology does not replace physiology. It extends it. It is this complementarity between the body and equipment that guides all our product development."
— Romane Benderradji, Communications Manager at G-Heat
Why choose G-Heat to extend your thermal balance?
When the body reaches its limits in the face of cold or heat, it's no longer a question of comfort. It's a question of being able to continue. G-Heat designs thermal equipment designed to intervene exactly where your natural thermoregulation fails.
- Active compensation, not a gimmick: our carbon filaments and cooling technologies (Jade Cool, Poly Cool, Phase Cool) target the areas where the body loses heat first—hands, feet, torso—to maintain your dexterity and alertness in the field.
- Designed by French engineers, validated in the field: each product is developed in-house by our R&D team and tested in real-world conditions—construction sites, motorcycle rides, industrial environments—before going into production.
- High-performance batteries in partnership with VoltR (French Tech): our lithium batteries offer several hours of battery life, support 500 charge cycles, and are part of an eco-design approach with reconditioned cells.
- Product ranges segmented by use, not by marketing: construction professionals, motorcyclists, cyclists, outdoor sports enthusiasts, people with Raynaud's syndrome — each thermal constraint has its own dedicated technical solution, with references that comply with PPE standards (EN 388) for professional environments.
- A brand recommended by leading retailers: G-Heat is distributed by Decathlon and Intersport and recognized by the French Handisport Federation — partners who only commit to reliable and proven equipment.
- Philosophy: extending the body, not replacing it: our devices do not short-circuit your thermoregulation. They complement it to keep you in your zone of equilibrium, where you remain lucid, precise, and operational — in all weather conditions.
Conclusion
The human body's thermoregulation system is remarkably precise. The hypothalamus controls it, thermoreceptors provide information, and blood vessels and muscles execute. Vasoconstriction at 36.8°C, shivering, sweating, vasodilation: each response has a single goal—to maintain your internal temperature at around 37°C.
But this system has its limits. When faced with extreme temperatures and prolonged exposure, the body eventually gives up. It is in this space—between the body's natural capacity and environmental constraints—that G-Heat comes in. Our equipment does not replace your physiology. It extends it, providing active heating or targeted cooling where the body is no longer sufficient. So you can keep going, whatever the weather.
FAQ
How can you tell if your body is regulating its temperature poorly?
There are several warning signs to look out for: extremities that turn white or blue in cold weather (possible Raynaud's syndrome), excessive or insufficient sweating, a persistent feeling of cold in a temperate environment, or significant variations in body temperature throughout the day. Certain health conditions—thyroid disorders, diabetes, circulatory diseases—impair the body's ability to regulate temperature. If these symptoms recur regularly, consult a healthcare professional. In addition, thermal compensation devices can help maintain your comfort on a daily basis.
At what temperature do G-Heat heated garments activate?
You decide. G-Heat heated clothing is controlled manually via a control button with three intensity levels (LED: white, blue, red). There is no automatic activation. You activate the heating according to how you feel and your level of activity. The carbon filaments reach their operating temperature within a few minutes of the battery being activated.
How long do G-Heat batteries last?
The battery life depends on the intensity level used and the type of battery. BATV01 batteries (jackets) offer several hours of battery life at medium intensity. BATG01 batteries (gloves), which are ultra-compact at 65 grams, are designed to last a day of activity when alternating between levels. All batteries support up to 500 charge cycles. Developed in partnership with VoltR (French Tech), they incorporate reconditioned lithium cells as part of an eco-design approach.
Can technical clothing replace natural thermoregulation?
No. And that's not their role. G-Heat equipment does not replace your body's physiological mechanisms: it complements them. A heated glove compensates for vasoconstriction in the extremities. A cooling vest helps the body evacuate excess heat. But your thermoregulation system continues to function normally. The goal is to extend your comfort zone so that your body doesn't have to resort to extreme responses—shivering, excessive sweating—which conserves your energy and your ability to stay active.
How to care for your G-Heat thermal clothing?
Always remove the batteries before washing. Wash heated clothing in cold water or at a maximum temperature of 32°F (30°C) on a delicate cycle. Tumble drying is strictly prohibited: the heat damages the carbon filament circuits. For Jade Cool cooling products, rinse with clean water after each use and leave to air dry. Store your batteries unplugged, charged between 40% and 50%, and fully charge them every three months during the off-season to preserve the lithium chemistry.
Which G-Heat technology should you choose for your activity?
The choice depends on your thermal constraints and context of use:
- Cold in motion (motorcycle, bicycle, hiking): carbon filament gloves and jackets with battery.
- Heat during intense sporting activity: Tech Cool technology works dry, without activation.
- Hot and static professional environments (construction sites, warehouses): Poly Cool or Phase Cool solutions for prolonged cooling.
- Raynaud's syndrome or circulatory disorders: Health ranges with thermal assistance devices suitable for everyday use.
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