In a nutshell 💡
- When temperatures rise, your heart rate increases to dissipate internal heat: blood vessels dilate, blood flows to the skin, and your resting heart rate can increase by 10 to 30 beats per minute.
- This normal reaction becomes risky in cases of dehydration, intense physical exertion, or cardiovascular vulnerability.
- Those most at risk: seniors, people with heart conditions, outdoor athletes, and construction workers.
- Regular hydration, adjusting exercise schedules, and using temperature-regulating gear can reduce the strain on the heart.
- G-Heat designs temperature-regulating gear to keep the body in its comfort zone, even in extreme heat.
145 beats per minute, at rest, under your umbrella. Your heart is working twice as hard.
This isn’t an abnormality: your body is mobilizing all its cardiovascular resources to keep you at 37°C while the air around you exceeds 35°C. Athletes training under the July sun, seniors on their balconies, construction workers on a site with no shade: they all experience the same invisible—yet very real—cardiac strain. According to Santé publique France, heat waves lead to a surge in emergency cardiovascular hospitalizations as soon as nighttime temperatures exceed 20°C for several consecutive days.
At G-Heat, we’ve been working since 2017 to design equipment that helps the body stay within its thermal equilibrium zone without extra effort. Our role isn’t medical—it’s technical. Heat pushes you to break down; we design to prevent that. Before we equip you, we need to understand what’s really happening in your body when the temperature rises—and why your heart pays the price.
How heat increases your heart rate
The Mechanism of Thermoregulation
Your body constantly produces heat, even at rest. At an internal temperature of 37°C, it must continuously dissipate this excess heat. When the outside temperature rises, this heat dissipation process intensifies. Sweating comes into play: as it evaporates on the skin’s surface, it dissipates heat. Effective, but demanding on the cardiovascular system.
Vasodilation: blood leaves the core for the skin
To dissipate heat, blood vessels near the skin dilate. Blood flows to the surface, cools down, and then returns to the organs. Imagine a car radiator: the hotter it is outside, the faster the fan spins to compensate. Your heart plays exactly this role of a forced pump. This massive redistribution of blood flow mechanically increases the heart rate.
Why the heart has to pump faster
Vasodilation causes a drop in blood pressure. To maintain it and continue supplying vital organs, the heart must increase its rate. The result: more beats per minute, even without moving. According to data from the INRS and Santé publique France, heart rate can increase by 10 to 30 beats per minute at rest during heat waves in healthy adults.
⚙️ Technology explained: JadeCool technology works through direct thermal conduction: the mineral fiber captures and dissipates body heat without requiring prior evaporation. Result: the skin cools down faster, the thermal gradient between the body and the environment decreases, and the heart no longer needs to work as hard to compensate. A JadeCool co oling neck wrap placed on the neck area acts directly on the blood vessels supplying the brain, where the effect is felt most quickly. Discover the full range of cooling neck wraps available in various colors.
See also: Heavy legs in hot weather: how to relieve them?
The real impact of heat on your cardiovascular system
Exercise at 20°C vs. exercise at 35°C: the big difference
At 20°C, your body handles the exertion without difficulty. At 35°C, the same physical activity requires much more work from the heart. The heart must both supply oxygen to the muscles AND cool the body. This dual task can increase the heart rate by 30 to 50 additional beats per minute, even at the same intensity of effort. For a runner, this is the difference between a controlled pace and exertion in the red zone.
Dehydration, low blood pressure, and cardiovascular risk
Sweating leads to a loss of water and minerals. If hydration does not compensate for these losses, blood volume decreases. The heart must pump harder to maintain blood pressure with a reduced blood volume. This mechanism is a major risk factor for cardiovascular events, including myocardial infarction in vulnerable individuals, as highlighted by Santé publique France’s epidemiological data on heat waves.
Moderate heat or heat wave: two levels of stress
Mild heat (25–28°C) remains manageable for most healthy adults. During a heatwave, with temperatures remaining above 32°C for several consecutive days, the body accumulates heat fatigue. Hot nights prevent cardiac recovery. The heart works continuously, without pause, unable to return to its normal resting rate.
Why the heart recovers more slowly in extreme heat
After exertion in hot weather, the heart rate takes longer to return to normal. Thermoregulation continues long after activity stops: the body continues to dissipate the heat accumulated in the tissues. Intense exertion in the middle of summer therefore requires a much longer recovery time than the same exertion performed in winter.
“The idea is not to overheat the body or cool it down abruptly, but to precisely compensate for what the environment takes away so that it can continue to function normally.”
— Gwenaël Fournet, Product Expert at G-Heat
To learn more: Heat rash in adults: how to relieve and prevent it?
Who is most at risk in the heat
Athletes and workers exposed to heat: a double risk factor
Runners, cyclists, construction workers, logistics staff: intense physical activity combined with extreme heat places a considerable strain on the cardiovascular system. Oxygen consumption increases, dehydration accelerates, and heatstroke can set in within a few hours. In its analysis of the Paris 2024 Olympic Games, INSERM highlights that athletes exposed to humid heat see their heart rates exceed critical thresholds well before the end of their exertion. For athletes, a PolyCool cooling vest worn during warm-up or recovery helps limit the rise in heart rate even before the start of exertion. Discover the full range of cooling vests designed for sports, work, or everyday use.
Seniors and aging adults: less effective thermoregulation
With age, the sensation of thirst diminishes and sweating becomes less effective. Older adults struggle more to dissipate heat: their heart rate increases faster and reaches higher levels in response to the same thermal stimulus. Dehydration sets in quickly, often without clear warning signs. A JadeCool XL cooling towel placed on the back of the neck or the forearms is enough to passively offset part of the heat load, without physical effort. The range of cooling towels offers several sizes, from compact to family-sized XL.
People with cardiovascular diseases
For people suffering from heart failure, coronary artery disease, or atrial fibrillation, heat is a significant risk factor. Certain common medications (diuretics, beta-blockers) alter the body’s response to heat and can mask the usual warning signs. Medical advice is essential before summer to adjust treatment and choose equipment suited to one’s condition.
Healthy young adults: a real safety margin, but not absolute
Healthy young adults have a robust cardiovascular system. Their hearts compensate more easily for rising temperatures. But this resilience can create a false sense of security during intense or prolonged exertion in direct sunlight, particularly during summer sporting events. A men’s cooling sports t-shirt by TechCool, or its women’s equivalent, actively wicks away sweat through breathable technical fabric and limits body overheating during exertion—a factor that increases the heart’s workload. Browse the full range of cooling T-shirts tailored to your activity.
💡 Real-world tip: For outdoor workers, don’t rely solely on breaks in the shade. A cooling vest worn from the start of your shift keeps your body temperature within its optimal range throughout the day. Cardiac recovery is much faster than waiting until the end of the day to rehydrate. Soak, wring out, wear: it takes less than thirty seconds to activate.
Must-read: JadeCool Technology: How Does It Work?
Warning signs you should never ignore
Palpitations, shortness of breath, and unusual dizziness
A heart racing for no reason, shortness of breath during moderate exertion, dizziness upon standing: these signs indicate excessive cardiovascular strain. Immediately move to a shaded or cool area, hydrate slowly, loosen your clothing, and monitor your condition. If symptoms persist beyond fifteen minutes, seek medical attention.
Chest pain and tightness: a medical emergency
Chest pain, a feeling of tightness, or pain radiating into the arm or jaw: this is a medical emergency. Call 911 immediately. Heat can trigger a heart attack in at-risk individuals, even without prior physical exertion.
Dizziness, confusion, dry skin: signs of heatstroke
Heatstroke is a life-threatening emergency. Signs to recognize immediately:
- Hot, dry skin (sweat is no longer being released).
- Body temperature above 40°C.
- Confusion, incoherent speech, loss of consciousness.
- Severe headaches and nausea.
- Very rapid pulse and rapid breathing.
When to see a doctor and when to call 911
See your doctor if you experience repeated palpitations, unusual shortness of breath, or extreme fatigue after a day of intense heat. Call 911 immediately if you experience chest pain, dizziness, confusion, or loss of consciousness. EVO PhaseCool cooling sleeves worn on the forearms provide discreet support between the first warning signs and seeking shelter: their microencapsulated thermal regulation works at room temperature, without needing to be activated.
⚠️ Important note: Never underestimate severe fatigue after a hot day, even without dramatic symptoms. This is often a sign that your heart has been working hard without being able to recover. Stay hydrated, sleep in a cool environment, and postpone any intense physical activity until the next morning, before 10 a.m. An abnormally high resting heart rate upon waking (more than 10 beats above your usual baseline) is a warning sign that should be taken seriously.
How to protect your heart during a heat wave
Hydration: Drink Before You Feel Thirsty
Thirst sets in late, especially in older adults and athletes, whose thirst receptors are overwhelmed by physical exertion. Drink regularly throughout the day, in small amounts. Water remains the best beverage. Avoid alcohol and limit coffee, as they worsen dehydration and increase heart rate.
Adjust your exercise schedule
Schedule physical activity early in the morning, before 10 a.m., or late in the day, after 7 p.m. During the hottest hours, stay indoors or in the shade. Intense exercise between noon and 4 p.m. during a heat wave poses a major cardiovascular risk, even for fit adults.
Active cooling: address the source, not the symptoms
Shade lowers the perceived temperature by 5 to 10 °C. A fan accelerates sweat evaporation. Regularly wetting your forearms, neck, and face helps maintain your body temperature within its optimal range. A TechCool cooling sports headband worn on the forehead absorbs sweat and promotes its evaporation thanks to its technical weave: less heat builds up in the head, so the heart has to work less.
Thermoregulatory gear tailored to your needs
Modern cooling gear helps keep the body within its thermal equilibrium zone, which directly reduces cardiovascular strain. Here are the solutions tailored to your situation:
| Profile | Suitable G-Heat equipment | Cardiovascular benefit |
|---|---|---|
| Outdoor athlete | TechCool cooling sports T-shirt + JadeCool cooling neck wrap | Limits the increase in heart rate during effort |
| Construction worker / job site | PolyCool cooling vest + EVO PhaseCool cooling sleeves | Reduces thermal load during an 8-hour shift |
| Senior / reduced mobility | JadeCool XL cooling towel + EVO PhaseCool cooling sleeves | Passive compensation without physical effort |
| Person with heart condition | EVO PhaseCool cooling sleeves | Stable thermal regulation without thermal shock |
Good daily habits during heat waves:
- Check the weather and plan your outings for cooler times of day (before 10 a.m. or after 7 p.m.).
- Drink 1.5 to 2 liters of water spread out over the day, without waiting until you’re thirsty.
- Wear cooling clothing suited to your activity and your needs.
- Wet your face, neck, and forearms regularly.
- Monitor your body’s signals: pulse, dizziness, unusual fatigue.
- Consult your doctor if you are taking cardiovascular medication.
“In the field, the best gear is the kind you forget you’re wearing. If you stop thinking about the heat, you’re 100% focused on your activity, and your heart is working within its optimal range. »
— Romane Benderradji, Communications Manager at G-Heat
Why choose G-Heat to better cope with the heat
When it comes to heat, it’s not just about comfort: it’s about continuing your activity safely. G-Heat designs personal thermoregulation gear so that the weather is no longer a reason to stop.
- Field expertise since 2017: our gear is validated by athletes, construction professionals, and people sensitive to extreme heat, throughout France.
- Four active cooling technologies: JadeCool, PolyCool, TechCool, and PhaseCool, each designed for a specific use (sports, static exposure, confined spaces, accessories).
- A pragmatic and honest approach: no empty promises, just applied physics to wick away body heat and keep the body within its comfort zone.
- A comprehensive range designed by body zone: vests, t-shirts, caps, arm sleeves, towels, neck coolers: every part of the body has its own tailored solution.
- Integrated sun protection: JadeCool fabrics combine active cooling with UPF 50+ protection, essential for limiting skin heat stress during prolonged exposure.
Conclusion
Heat isn’t just a matter of comfort: it’s a real strain on your cardiovascular system. Understanding why your heart rate increases is the first step toward better managing it. Hydration, adjusting your workout schedule, active cooling, and thermoregulatory gear: you now have the right habits to protect your heart during heat waves.
Discover our full range of cooling clothing to keep moving, working, and enjoying the summer without putting excessive strain on your heart.
Whatever the weather. G-Heat, in all weather conditions.
FAQ
At what temperature does heat become dangerous for the heart?
Above 30°C, the heart works harder in most healthy adults. At 35°C and above, especially in high humidity, cardiovascular risk increases significantly. For older adults or those with cardiovascular disease, caution is advised starting at 28°C. The INRS and the Ministry of Health recommend paying special attention from the very first days of a heat wave.
Is a heart rate that increases with the heat always a cause for concern?
No. An increase of 10 to 20 beats per minute at rest is a normal bodily response to heat. It becomes a cause for concern if the heart rate exceeds 100 beats per minute at rest, if it is accompanied by dizziness, shortness of breath, or chest pain, or if it persists after cooling down and rehydrating.
Is it safe to exercise when the temperature is over 30°C?
Yes, provided you adjust the intensity, timing, and equipment. Opt for early morning or evening workouts. Reduce intensity by 20 to 30%. Drink before, during, and after exercise. Wear cooling technical clothing and a suitable hat. Avoid intense exercise between noon and 4 p.m.
Which G-Heat products help reduce cardiac strain in extreme heat?
PolyCool cooling vests maintain core body temperature, where vital organs are concentrated. TechCool cooling sports T-shirts wick away sweat through breathable technical fabric to limit overheating during exercise. EVO PhaseCool cooling sleeves regulate forearm temperature without prior activation. The JadeCool neckband acts directly on the cervical vessels that supply the brain.
How do G-Heat cooling textiles work?
G-Heat utilizes three distinct physical principles: mineral conduction (JadeCool, rapid heat dissipation through contact), water retention and gradual evaporation (PolyCool, long-lasting), and phase-change microencapsulation (PhaseCool, stable thermal regulation at room temperature). TechCool, on the other hand, works through a technical weave that promotes the natural evaporation of sweat, without requiring activation. These four mechanisms all aim for the same goal: to maintain the body within its thermal equilibrium zone to relieve the heart’s workload.
Can people with heart conditions use cooling gear?
Yes, and it is even recommended to reduce cardiovascular strain during hot weather. Passive cooling textiles (JadeCool, PolyCool) do not cause any sudden thermal shock: they simply support natural thermoregulation. However, consult your doctor or cardiologist before summer to ensure your gear is suitable for your condition.
How should you care for cooling gear to keep it effective?
Wash your cooling fabrics in cold water or at a maximum of 30°C, without fabric softener (which clogs the active fibers). Avoid the dryer. To reactivate a JadeCool or PolyCool fabric, submerge it in water, wring it out firmly, then shake it to activate the fibers. Regular care ensures effectiveness season after season.
Sources and references
[1] “Heat: Accidents and Health Effects”, INRS
[2] “Paris 2024 Olympics: Heat Wave Hits Sports”, INSERM
[3] “Weekly Epidemiological Bulletin No. 7, 2025”, Santé publique France
[4] “Heat: Key Takeaways”, INRS
[5] “Heat Waves and Their Effects on Health”, Ministry of Health
[6] “What Measures Can Be Taken to Prevent Heat-Related Risks?”, Santé publique France
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