Whether you're under a blazing sun or exposed to freezing temperatures, your body wages an invisible and constant battle to maintain a stable internal temperature of around 37°C . This feat is no accident: it relies on thermoregulation , a vital and highly complex regulatory system. Mastering its function will not only allow you to optimize your athletic performance but also protect your health in the face of extreme temperatures.
What is thermoregulation?
There Thermoregulation refers to all the processes that keep your internal temperature stable around 37°C, regardless of environmental conditions.
This reference value is not always fixed.
- Daily fluctuations of ± 0.25 to 0.5 °C occur throughout the day according to the circadian rhythm.
- Monthly variations of +0.3 to 0.5 °C are induced by hormones in the luteal phase of the menstrual cycle in women.
It is important to note that the human body is divided into two thermal zones :
- The central core (brain, heart, liver), characterized by a stable temperature.
- The periphery (skin, extremities), which adapts to external conditions and exhibits more pronounced variations. This is referred to as peripheral or cutaneous temperature .
How does thermoregulation work?
Thermoregulation relies on three closely linked components: thermoreceptors (thermal sensors), the hypothalamus (regulatory center) and effectors (blood vessels, sweat glands and muscles).
The body's thermal sensors
The body has a network of strategically distributed thermoreceptors to detect temperature variations.
Cutaneous thermoreceptors , located on the surface of your skin, detect changes in ambient temperature . Two types coexist: receptors sensitive to heat (≈ 30–43 °C) and those sensitive to cold, which respond between 10 and 35 °C.
Central thermoreceptors , primarily located in the hypothalamus, but also in the spinal cord and certain internal organs, control your blood temperature . A variation of just 1°C is enough to trigger a thermoregulatory response.
This dual surveillance, peripheral and central, creates an early warning system against thermal threats.
The regulatory mechanisms
The hypothalamus continuously receives information from the thermoreceptors and compares the measured temperature to the set point of 37°C. If a deviation is detected, it immediately triggers the action of the appropriate effectors .
Faced with excessive heat, it activates mechanisms such as:
- Vasodilation : your blood vessels dilate to increase blood flow to the skin and dissipate heat .
- Sweating : your sweat glands produce sweat to cool the skin through evaporation.
In cold weather, it activates:
- Vasoconstriction : your blood vessels contract to limit loss.
- Shivering : your muscles contract involuntarily to generate heat.
- Brown adipose tissue : your body produces heat without shivering thanks to non-shivering thermogenesis.
The balance between heat production and heat dissipation
Maintaining your body temperature relies on a constant balance between heat production ( thermogenesis ) and its dissipation ( thermolysis ).
Thermogenesis primarily comes from your basal metabolic rate and muscle activity. More 75% of the energy produced by your muscles is converted into heat and raises your core temperature, as confirmed by an article published on NCBI Bookshelf.
Heat loss occurs approximately 90% through the skin, via four main mechanisms: radiation (65% at rest), convection (10–15%), evaporation (20% at rest, up to 85% during exertion) and conduction (2%).
Factors that influence thermoregulation
Environmental conditions
THE Climate and seasonal variations play a determining role:
- Room temperature : the further it is from 37°C, the more mechanisms your body has to mobilize to maintain balance.
- Humidity : it limits the evaporation of sweat.
- Wind : it increases losses by convection.
- Exposure to the sun : it increases the heat load by radiation.
Physiological characteristics
Several individual factors influence your thermoregulatory abilities.
Age plays a crucial role. Infants lose heat rapidly due to their immature immune system and large body surface area. Older adults have reduced heat perception and thirst sensation, increasing their risk in extreme temperatures.
Body composition also influences regulation. High muscle mass increases heat production, while a high proportion of fat improves insulation but hinders heat dissipation.
Gradual acclimatization over 7 to 14 days optimizes sweating and heat tolerance. Certain medical conditions (diabetes, cardiovascular diseases) and medications (beta-blockers, diuretics) disrupt thermoregulation. Finally, your voluntary actions complement this automatic regulation: seeking shade, adjusting your clothing, and staying hydrated.
Hydration and nutrition
A A review published in Comprehensive Physiology shows that dehydration and heat stress reduce blood volume and cutaneous blood flow. This decrease limits heat dissipation and promotes an increase in core temperature during exercise.
An electrolyte deficiency (sodium, potassium) also compromises your ability to sweat effectively and regulate your temperature.
Food provides the energy needed for thermogenesis. Carbohydrates and lipids serve as fuel to produce metabolic heat.
Thermoregulation and sport: a performance issue
The key role during the effort
During intense physical activity, a large portion of your muscle energy is converted into heat . To prevent overheating, the body increases sweating, its primary mechanism for heat dissipation. This process is effective, but it leads to rapid fluid loss.
The risks of poor thermal regulation
As this shows A meta-analysis published in the British Journal of Sports Medicine found that a loss of approximately 2% of your body weight due to dehydration can reduce your endurance capacity. It also impairs cognitive function: attention, alertness, and memory decrease, and this can lead to the early onset of muscle cramps and fatigue. In extreme cases, severe hyperthermia , induced by a lack of water, can progress to... Heat stroke from exertion , a life-threatening emergency.
How to optimize your thermoregulation during training
In practice, gradually expose yourself to hot conditions for 7 to 14 days. Drink Drink 400 to 600 ml of water two hours before exercise, then 150 to 200 ml every 15 to 20 minutes. For activities lasting longer than an hour, choose drinks with electrolytes. Wear light-colored, loose-fitting, and breathable clothing.
Thermoregulation disorders
Hypothermia: body temperature below 35°C, symptoms and what to do
Hypothermia is characterized by intense shivering, mental confusion, a slowed heart rate, and altered consciousness. Gradually warm the victim in a sheltered location , remove wet clothing, and cover them. Seek immediate medical attention for any moderate to severe hypothermia .
Hyperthermia: heatstroke, severe dehydration, life-threatening emergency
Heat stroke represents the most serious form of hyperthermia. It occurs when the body's heat dissipation mechanisms become insufficient, leading to a rapid rise in body temperature, often above 39.5°C , accompanied by neurological disorders (confusion, altered consciousness) and sometimes organ failure.
This situation is a life-threatening emergency and requires immediate cooling and rapid medical attention.
How to promote good thermoregulation on a daily basis
The importance of hydration
Drink regularly throughout the day. Clear urine is a simple indicator of good hydration.
Anticipate your water needs in case of extreme weather conditions or prolonged physical activity.
Opt for drinks containing electrolytes to compensate for sodium loss during prolonged exercise and/or in hot weather.
Adjusting your diet
Consume balanced meals combining complex carbohydrates (stable energy production), proteins (muscle mass), fruits and vegetables (hydration).
Adjust according to the season : fresh foods in hot weather, increased calorie intake in cold weather.
Taking care of one's environment and recovery
Use air conditioning or ventilation during heat waves. Close shutters during the hottest hours. Wear several thin layers in winter and lightweight fabrics in summer. Sufficient sleep is crucial for temperature regulation.
Testimonials and studies: thermoregulation in athletes
During the At the 2019 World Athletics Championships , heat-acclimated runners showed better thermal tolerance and performance than non-acclimated runners.
A A scientific review compiling numerous studies on trained endurance athletes indicates that heat acclimatization increases sweating , optimizes skin circulation and improves heat dissipation during exertion in hot conditions.
These observations highlight that thermoregulation is not just a physiological mechanism , but a key factor that directly influences the performance and safety of athletes exposed to heat.
FAQ: Everything you need to know about thermoregulation
What triggers thermoregulation?
Thermoreceptors detect temperature changes and transmit this information to the hypothalamus, which activates the appropriate effectors.
Why do we sweat when it's hot?
The evaporation of sweat consumes thermal energy, thus lowering your body temperature.
Can thermoregulation become disrupted?
Yes. Dehydration, certain medical conditions (diabetes) and certain medications impair thermoregulatory abilities.
Does sport improve thermoregulation?
Training optimizes your abilities: earlier and more efficient sweating, increased plasma volume, better tolerance to dehydration.
What role does hydration play in thermoregulation?
Water enables the production of sweat and maintains the blood volume necessary for heat transport.
Conclusion: a vital balance to preserve
Thermoregulation keeps your body temperature stable despite environmental and metabolic variations. The hypothalamus constantly orchestrates a delicate balance between heat production and dissipation, mobilizing thermoreceptors, blood vessels, sweat glands, and muscles. Understanding these mechanisms allows you to optimize your athletic performance and preserve your health.
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