VoltraExercising in the heat: heat exhaustion, heat stroke, and what to drink
Train in the cooler hours or indoors, and drink regularly rather than waiting for thirst [1] [6]. Heat exhaustion (heavy sweating, cold pale skin, nausea, dizziness) means stop, get somewhere cool and sip cold water [2]. Heat stroke (a body temperature of 40 °C or more, with confusion or collapse) is an emergency: call an ambulance, cool the person down, and don't give them anything to drink [3].
Heat exhaustion or heat stroke?
| Heat exhaustion | Heat stroke | |
|---|---|---|
| Skin and sweat | Heavy sweating; cold, pale skin [2] | Hot, red and damp skin [3] |
| Other signs | Nausea or vomiting, cramps, tiredness, dizziness or fainting, headache, weak pulse [2] | Temperature of 40 °C or more, strong fast pulse, headache, dizziness, nausea, hallucinations, loss of consciousness [3] |
| First aid | Move somewhere cool, loosen clothes, cold compresses on the neck or armpits, spray with water, cold water to drink [2] | Call an ambulance at once, move somewhere cool, cool with cold compresses and cold water, nothing to drink [3] |
| Get medical help | If they vomit, get worse, or symptoms last over an hour [2] | Always: it can kill [3] |
Saudi Arabia's health ministry pages don't all describe heat stroke the same way: one lists damp skin [3], another dry skin and sweating [5], and the WHO lists stopping sweating as a warning sign [8]. So sweating doesn't rule heat stroke out; confusion, collapse or a very high temperature mean call for help.
The WHO's heat-stroke steps: call emergency services first, then move the person into shade or air conditioning, put cold, wet cloths on them, and use ice packs and fans, or a cold-water bath if that's possible and safe [8]. At sports events with medical teams, the IOC's rule is to cool the athlete on site before moving them [9]. Never give a drink to someone who isn't fully conscious [5].
Heat cramps
Heat cramps are painful spasms, often in the legs, in people who sweat heavily during hard activity: sweat drains salt and water [4]. Stop, get somewhere cool, drink water and wait for the cramps to pass; get medical help if they last an hour or more, or if you have heart problems or are on a low-sodium diet [4].
How much to drink
- Before and during: drink before, during and after exercise, especially in hot weather, in small amounts often rather than large amounts less often [1]. People sweat about 0.5 to 2.0 litres an hour when they exercise [1].
- Don't wait for thirst: Saudi Arabia's health ministry says thirst only starts once you've lost about 2% of your body weight [1].
- Check your urine: plenty of clear urine means you're getting enough; small amounts of dark yellow urine mean you're dehydrated [1].
- Weigh yourself before and after a session to learn your sweat rate [11]. The aim is to lose no more than 2% of your body weight [11]: 1.4 kg for someone of 70 kg (calculated).
- Don't overdo it. Recreational exercisers on long sessions should be careful not to overdrink [10]: drinking too much plain water can dilute the blood's sodium [9], and gaining weight during a long event is a warning sign [10].
- Afterwards: the ministry advises about 1.25 to 1.5 litres for each kilogram lost [1], so 1.25 to 1.5 litres if you lost 1 kg (calculated); a heat consensus says replacing 100 to 120% of the loss is more realistic [10].
Water or a sports drink?
Water is the best choice unless you train hard for more than an hour [1]. Sports drinks, with glucose and electrolytes such as sodium, help endurance sessions of 60 minutes or more, but they're sugary, adding calories and risking tooth decay, so they suit high-level endurance sport or very heavy sweating [1]. Energy drinks aren't designed to replace the electrolytes lost in sweat and may contain stimulants such as caffeine [1]. Milk works as a recovery drink after exercise [1].
For sessions over an hour, a 2015 heat consensus suggests drinks with 0.5–0.7 g of sodium per litre and 30–60 g of carbohydrate an hour [10]; two of its authors have had funding or panel ties to the Gatorade Sports Science Institute [10].
Preventing it
- Avoid going out and strenuous activity in the hottest part of the day, and stay in the shade: in the sun, the temperature you feel can be 10 to 15 °C higher [6].
- Get used to the heat gradually: acclimatisation takes repeated exercise in the heat over 1–2 weeks [10].
- Young, healthy people are at risk too when they exert themselves in hot weather [5].
- Some medicines raise the risk, including antihistamines, antidepressants, diuretics, some acne medicines and some blood pressure medicines [7]. Ask your doctor if you take any.
- For walking, see our Japanese walking guide, and for daily needs, how much water you need.
In Voltra
Log water on the Eat tab. You can also turn on hydration reminders in your notification settings.
Frequently asked
What's the difference between heat exhaustion and heat stroke?
Heat exhaustion brings heavy sweating, cold pale skin, nausea and dizziness; move somewhere cool and drink cold water. Heat stroke means a body temperature of 40 °C or more with confusion or collapse: call an ambulance and cool the person, and give them nothing to drink.
Should I drink water or a sports drink in the heat?
Water, unless you train hard for more than an hour. Sports drinks help long endurance sessions but add sugar and calories; energy drinks aren't made to replace electrolytes.
How much should I drink after a workout?
Saudi Arabia's health ministry advises about 1.25 to 1.5 litres for each kilogram of weight lost in sweat. Weigh yourself before and after to know.
When is it too hot to train outside?
The WHO advises avoiding strenuous activity in the hottest part of the day. In a Gulf summer, train early, late or indoors, and build up over 1–2 weeks.
Sources
- وزارة الصحة، المملكة العربية السعودية (١٤٤٧ هـ). ترطيب الجسم والرياضة. In Arabic.
- وزارة الصحة، المملكة العربية السعودية (١٤٤٧ هـ). الإسعافات الأولية: الإجهاد الحراري. In Arabic.
- وزارة الصحة، المملكة العربية السعودية (١٤٤٧ هـ). الإسعافات الأولية: ضربة الشمس. In Arabic.
- وزارة الصحة، المملكة العربية السعودية (١٤٤٧ هـ). الإسعافات الأولية: تشنجات العضلات الناتج عن ارتفاع الحرارة. In Arabic.
- وزارة الصحة، المملكة العربية السعودية (١٤٤٧ هـ). حرارة الصيف. In Arabic.
- World Health Organization (2026). Heat and health (fact sheet, 31 July 2026). Also in Arabic.
- وزارة الصحة، المملكة العربية السعودية (١٤٤٨ هـ). أحوال الصحة في الموجات الحارة. In Arabic. Risk factors.
- World Health Organization (2024). What to do if you see signs of heat stroke
- Racinais S, Hosokawa Y, Akama T, et al. (2023). IOC consensus statement on recommendations and regulations for sport events in the heat. Br J Sports Med 57(1):8–25. Exertional heat stroke; hydration.
- Racinais S, Alonso JM, Coutts AJ, et al. (2015). Consensus recommendations on training and competing in the heat. Br J Sports Med 49(18):1164–73. Hydration and acclimatisation; funding statement.
- American College of Sports Medicine; Sawka MN, Burke LM, Eichner ER, et al. (2007). Exercise and fluid replacement (position stand). Med Sci Sports Exerc 39(2):377–90. Abstract.
Sources checked on 30 September 2026.
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