Everything You Need to Know About Fluids When Exercising in Heat
Baseline: 30–35 ml of water per 1 kg of body weight. For a person weighing 80 kg — ~2.5 liters per day.
With exercise: +500–1000 ml for each hour of training. On a hot day (above 30°C) — +50%.
Practical test: Weigh yourself before and after training. Every 1 kg lost = 1.5 liters of fluids that need to be replaced.
Drinking too much plain water without electrolytes is dangerous — hyponatremia (low sodium in the blood) can develop. Symptoms: nausea, headache, confusion. In workouts longer than 1 hour, always use electrolytes.
On hot days, outdoor training is not only a matter of hydration but also skin protection. Use a water-resistant sunscreen, reapply it after heavy sweating, and, if possible, avoid the midday sun. Light-colored clothing and a hat help prevent overheating and sunstroke. These measures not only protect your health but also allow you to train longer and with better quality.
It is better to schedule intense workouts for early morning or late evening, when the temperature is lower. If you have to exercise during the day, reduce intensity and rest longer in the shade. The body acclimatizes to heat gradually — during the first weeks of the hot season, do not rush to chase personal records. Listen to your body's signals: dizziness or nausea is a sign to stop and cool down.
Drink before, during, and after training, not only when thirst strikes. During prolonged exercise in the heat, water alone may not be enough — electrolytes are also lost. Light yellow urine is a good sign that you are sufficiently hydrated. Read more about water needs in the water guide.
Recognizing overheating as early as possible is worthwhile. The first signs are heavy sweating, thirst, muscle cramps, and dizziness. If you feel these symptoms, stop, move into the shade, cool your body, and drink in small sips. Heat stroke — a more serious condition with hot skin and confusion — requires emergency help, so it is better to avoid it by stopping training in time.
When you sweat intensely, you lose not only water but also electrolytes — sodium, potassium, and other minerals. For long workouts in the heat, water alone may not be enough, so it is worth having an electrolyte drink or a salted snack. Do not drink large amounts of carbonated or very sweet drinks — they can cause discomfort. The best choice is water with a pinch of salt or a special electrolyte mix.
During hot weather, appetite often decreases, so choose lighter but nutritious food: fruits, vegetables, lean proteins, and light dishes. Heavy, fatty food before training can cause discomfort. Do not forget salt, as you lose it through sweating — lightly salted food will help maintain electrolyte balance. Eat in smaller portions but more often.
During the hottest part of the day, roughly from 11:00 to 16:00, it is better to avoid intense outdoor exercise. Early morning is the coolest and cleanest air; evening is also suitable, just try to finish at least a couple of hours before sleep. By choosing a consistent time, you will find it easier to maintain a routine and avoid the peak heat and strongest sun.
First signs: thirst, dark urine, dry mouth. Later: headache, muscle cramps. Urine should be light yellow.
Yes! Hyperhydration (hyponatremia) is dangerous. Symptoms: nausea, confusion. Always use electrolytes during long workouts.
Early in the morning (until 10 val.) or in the evening (after 18 val.). Avoid 11–16 valandos, when the UV index is highest.
Want to learn more? We recommend these sources:
📱 Apps: Strava, Nike Training Club, MyFitnessPal — track your progress and nutrition.
: Sports nutrition and training literature in Lithuanian and English.
🎓 Consultations: Consult a sports nutrition specialist or personal trainer for an individual plan.
⚠️ Important: All information is for informational purposes only. Before starting a new training or nutrition program, consult a doctor or a certified specialist.