Healthy Living in Hot Weather: Practical Tips

9 min read

In Gulf climates, anyone who exercises or works outdoors faces the same question for half the year: how do I stay active in this heat without harming myself? The body has a remarkable mechanism for adapting to heat called “heat acclimatization,” and a massive quantitative review published in the journal Comprehensive Physiology in 2025 (led by Julien Périard at the University of Canberra) synthesized the findings of 211 studies covering 2,587 participants to precisely determine how many days the body needs to adapt, and exactly what changes. The bottom line: within 7 to 10 days of gradual heat exposure combined with exertion, exercising heart rate drops by roughly 17 beats per minute, core body temperature decreases, sweating begins earlier and more heavily, and plasma volume expands by around 5.6% — all changes that make moving in the heat safer and less exhausting.

What does heat do to your body during exercise?

When you exert effort in the heat, your body faces a competition for blood: the muscles need it to deliver oxygen, and the skin needs it to carry heat to the surface and dissipate it through sweating. This “cardiovascular strain” raises heart rate, reduces the volume of blood returning to the heart, accelerates fatigue, and lowers performance. As water is lost through sweat, blood volume drops further, worsening the cycle. This is why someone who isn’t acclimatized feels that a routine workout becomes “impossible” in the first days of a hot summer — it isn’t weakness, it’s physiology.

In addition, exertion in heat raises stress hormone secretion, accelerates the depletion of muscle glycogen, and increases lactic acid production at a given intensity compared with moderate weather. In other words, the exercise itself “feels” heavier, and perceived exertion rises even if speed or load stay constant. Understanding this helps set realistic expectations: it’s normal to reduce intensity or distance by 10-20% in the first hot days, and to build back up gradually as you acclimatize rather than forcing winter numbers.

How does the body adapt? The numbers from the review

The researchers analyzed different acclimatization protocols and arrived at a clear quantitative picture:

Heart rate: resting heart rate drops by about 5 beats, exercising heart rate by about 17 beats, and most of the improvement is complete within roughly 8 days.
Core body temperature: decreases by about 0.19°C at rest and 0.43°C during exercise, with additional benefit for longer sessions.
Sweating: the rate increases by about 163 ml per hour, and begins at a lower body temperature (i.e., earlier) — this is the most important improvement for cooling.
Plasma volume: expands by about 5.6% during the first days, increasing blood volume and improving cardiac performance.
Performance: time to exhaustion improves by about 49%, and time-trial performance by about 3.1%.

Most of these adaptations appear within a 7-10 day window, and after about 10 sessions the additional benefit clearly diminishes — with the exception of hemoglobin mass, which continues improving with longer protocols (12 days or more).

How do you acclimatize in practice?

You don’t need a laboratory heat chamber. The principle: gradual heat exposure combined with light-to-moderate exertion, daily or on most days, for 7-14 days:

Start with short sessions (20-30 minutes) at low intensity during relatively hot times (not the hottest), then gradually extend to 60-90 minutes.
Raise intensity slowly over the days; the goal is to raise body temperature slightly and stimulate sweating, not to exhaust yourself.
Stick with it daily as much as possible; a break of two or more days slows the adaptation.
Practical alternatives: a moderate sauna session or a warm bath after light exercise can contribute to acclimatization for those who can’t train outdoors.
Maintain hydration throughout the process, since dehydration reduces plasma volume expansion, one of the most important gains of acclimatization.

The benefit gradually fades after stopping: part of it is lost within one to two weeks of no heat exposure, so anyone returning to a hot environment after a vacation in a cold climate needs a mini re-acclimatization.

Why is humidity sometimes more dangerous than heat?

The body’s primary cooling during exertion relies on sweat evaporating from the skin; every gram of sweat that evaporates carries heat away with it. But evaporation slows considerably when the surrounding air is saturated with water vapor. That’s why a day at 35°C with 70% humidity can be more dangerous for someone exercising than a day at 42°C with dry air. In Gulf coastal cities specifically — where humidity rises in summer — the challenge doubles: sweat pours heavily without cooling effectively, so the body loses water and salts without adequate cooling benefit, and its internal temperature rises quickly. Monitoring the “heat index” or “wet-bulb temperature” is better than relying on the thermometer reading alone.

What changes in the body with acclimatization?

The adaptations tracked by the review aren’t improvements “in fitness” but in “heat management.” Plasma volume expansion means more blood filling the heart and vessels, reducing the competition between muscles and skin for blood and lowering heart rate. Sweating starting at a lower body temperature means the body activates its cooling system earlier, before its internal temperature rises much. And an increased sweat rate along with “salt conservation” in sweat (sweat becomes less salty after acclimatization) means better cooling with less salt loss. Together, these changes lower body temperature during exertion itself, delay fatigue, and reduce the risk of heat illness. These are relatively rapid adaptations because they depend on changes in fluid volume and hormones rather than slow tissue rebuilding.

Common myths about heat

“Drink only when thirsty”: thirst is a relatively delayed signal, especially in older adults whose sense of thirst weakens; regular drinking in small amounts during prolonged exertion in heat is better. On the other hand, excessive water without salts during very prolonged effort can dangerously dilute blood sodium (“exertional hyponatremia”), so balance is what’s needed, not excess in either direction.

“Salt tablets are essential”: for most activities, a balanced diet and a moderate sports drink are enough to replace salts; concentrated salt tablets can irritate the stomach and are only needed by a few very-long-endurance athletes in extreme conditions.

“Heavy sweating is a sign of fitness”: early, regular sweating after acclimatization is beneficial, but excessive sweating itself is not a goal; sweat suits and excessive layering to lose “water weight” is a dangerous practice that causes dehydration and heat strain.

Children and heat

Children acclimatize more slowly than adults, sweat relatively less, and have a large body surface area relative to their mass, so they gain heat from their surroundings faster. They shouldn’t engage in intense activity at peak heat, should be encouraged to drink fluids regularly even without asking, dressed in light clothing, and given rest breaks in the shade. A child — or an animal — should never be left in a closed car even for a few minutes; the temperature inside rises to lethal levels very quickly.

Recognizing heat illness — the most important thing for safety

Acclimatization reduces the risk but doesn’t eliminate it. Heat illnesses range from mildest to most dangerous:

Heat cramps: painful muscle spasms during exertion, often with sodium and fluid deficits. Treatment: stop, cool down, drink fluids containing salts.

Heat exhaustion: severe fatigue, dizziness, nausea, headache, heavy sweating, cool clammy skin, rapid pulse, elevated body temperature but often below 40°C. Treatment: move immediately to a cool place, lie down and elevate the legs, cool the skin with water and fans, drink fluids. No improvement within 30 minutes requires emergency care.

Heat stroke: a life-threatening emergency. The defining sign: altered consciousness (confusion, delirium, seizures, loss of consciousness) with very high body temperature. Sweating may stop or continue. Action: call emergency services immediately, and begin aggressive cooling without delay (cold water immersion if possible, or spraying water and covering with wet towels with ventilation). Every minute of delay in cooling increases the risk of permanent damage.

Who is most at risk?

Older adults (weaker sweating response and reduced sense of thirst), young children, pregnant women, people with heart, kidney, or diabetes conditions, and those taking certain medications (diuretics, some blood pressure and antidepressant medications, and antihistamines). Also outdoor workers, athletes who push themselves despite symptoms, and those who exert intense effort in the first days of a heat wave before acclimatizing. For these groups, extra caution and adjusting timing and intensity are not optional.

Smart options for staying active in extreme heat

When temperatures exceed safe limits for outdoor activity, the solution isn’t to stop for months but to relocate: exercise at dawn or after sunset when temperatures drop and midday humidity is absent, or inside air-conditioned gyms, pools, and centers, or walk in enclosed corridors. Wear light-colored, loose, quick-drying clothing, use sunscreen, and plan your route near water sources and shade. Monitor the heat and humidity index together; high humidity prevents sweat evaporation and makes “moderate” heat dangerous. And tell someone your route and expected return time if exercising alone outdoors, and carry a charged phone.

Limitations of the evidence — honestly

First, 91% of participants in the major review were male, and 60% of the studies had no control group, so the numbers are good estimates rather than absolute facts, and responses may differ among women and older adults. Second, many studies were on healthy young athletes, so generalizing acclimatization protocols to patients and older adults requires medical supervision. Third, “acclimatization” improves endurance and comfort, but it doesn’t make exertion in extreme heat completely safe; adjusting timing and intensity remains necessary. Fourth, most data comes from controlled experimental settings that differ from unpredictable real-world heat.

Practical steps

Dedicate 7-14 days to acclimatization at the start of each summer or when returning from a cold climate: short, light sessions gradually extended.
Expect the first hot days to be the hardest; performance clearly improves after a week of regular exposure.
Shift timing and location instead of stopping activity seasonally: dawn, evening, or indoors with air conditioning.
Remember the signs of exhaustion and heat stroke: altered consciousness with high temperature = emergency and immediate cooling, no waiting.
Watch humidity, not just heat: high humidity makes moderate heat dangerous because it prevents sweat evaporation.
Be extra cautious if you’re in a vulnerable group (older age, pregnancy, chronic illness, certain medications) and consult your doctor about safe activity limits.
Don’t ignore early symptoms: dizziness, nausea, and headache during exertion in heat are signals to stop, not signs of “weakness” to push through.

The bottom line is that the body can adapt to heat within one to two weeks of gradual exposure, and this adaptation is quantitatively documented and improves both safety and performance. But acclimatization complements caution, not replaces it: adjusting timing and intensity, knowing the warning signs, and paying attention to vulnerable groups remain the foundation of a healthy, active life in hot climates. Investing in two weeks of acclimatization at the start of each summer saves the body weeks of suffering, and turns heat from an obstacle that halts activity into a condition that can be handled intelligently.

Sources

The information in this article is for educational purposes only and does not substitute professional medical consultation, and in cases of heat emergencies, seek emergency medical help immediately.

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