You run, you sweat, you're thirsty. You drink liters of water. And you feel awful: cramps, nausea, dizziness. What went wrong? You drank too much, or too little, or at the wrong time, or without the right electrolytes. Hydration in sports isn't as simple as "drink when you're thirsty."

Professional athletes have nutritionists who calculate every milliliter. You don't. But you can learn the basic rules and apply them. The difference between peak performance and collapse often comes down to proper hydration.

Why sports increase your water needs

When you exercise, your muscles produce heat. To keep you from overheating, your body sweats. The sweat evaporates and cools you down. Perfect process, but it costs water and electrolytes.

In an hour of intense exercise, you can lose 0.5-2 liters of sweat. It depends on: intensity, temperature, humidity, and your fitness level. Well-trained athletes sweat earlier and more (it's efficiency), so they lose more fluids.

If you lose 2% of your body weight in fluids, performance drops 10-20%. If you lose 5%, you risk cramps and collapse. For a 70 kg athlete, 2% is just 1.4 liters. You can reach that in an hour of summer running.

Before training: start hydrated

Don't start already dehydrated. Drink 400-600 ml of water 2-3 hours before training. This gives your body time to hydrate and eliminate excess before you begin.

Don't drink liters right before: you'll feel heavy, your stomach full, and you'll need to urinate during the activity. Timing matters.

Check your urine before heading out. Light straw yellow = perfect. Dark yellow = drink more before starting. Clear = you've drunk too much, wait for your body to balance.

During training: little and often

The basic rule: drink 150-250 ml every 15-20 minutes. Small amounts spread out. Your stomach can absorb about 800-1000 ml per hour. If you drink more, it sits in your stomach and makes you feel sick.

Don't wait until you're thirsty. When you feel thirsty, you're already 1-2% dehydrated. Drink at regular intervals, even if you don't feel the need.

If the activity lasts less than 60 minutes: water alone is fine. If it lasts more than 60 minutes: you need water plus electrolytes (sodium, potassium). Sweat carries away salts, water alone isn't enough.

What to drink: water, sports drink, or something else?

Sports drinks (Gatorade, Powerade, etc): contain water plus sugars plus electrolytes. Useful for activities longer than 60-90 minutes. The sugars provide energy, the electrolytes replace lost salts.

Water plus salt: an economical alternative to sports drinks. Add a pinch of salt to 500 ml of water. Provides sodium without sugars. Works fine if you don't need extra energy.

Water with lemon and honey: natural sugars plus potassium plus some sodium. Less effective than professional sports drinks, but better than plain water for long activities.

Chocolate milk: excellent post-workout for recovery. Has protein plus carbs plus electrolytes. Many studies show effectiveness equal to sports drinks for recovery.

Energy drinks (Red Bull, Monster): NO during sports. Too much caffeine, too much sugar, they dehydrate you. Use them only as pre-workout in small amounts, not during.

After training: fluid recovery

Weigh yourself before and after training. The difference is water lost through sweat. Every kg lost = 1 liter to replace. But not all at once: spread it over the next 2-3 hours.

Practical rule: drink 150% of the weight you lost. If you lost 1 kg, drink 1.5 liters over the next 3 hours. The extra 50% compensates for urine losses during recovery.

Always add electrolytes to your recovery. Water plus salty food (prosciutto, parmesan, salted crackers) or sports drink or supplements. Sodium is essential for retaining the water you drink.

Signs of dehydration during sports

Intense thirst: you're already 2% dehydrated. Slow down, drink immediately, resume gradually.

Muscle cramps: lack of sodium, potassium, magnesium. Stop, drink water with electrolytes, massage the muscle, wait for it to pass. Don't push through.

Dizziness, confusion: severe dehydration. Stop immediately, get into shade, drink small sips, ask for help if it doesn't improve in 10-15 minutes.

Nausea, vomiting: too much water too fast (full stomach) or hyponatremia (too much water without salts). Stop, don't drink for 20-30 minutes, resume with salt water.

Very little and dark urine after training: you drank too little. Rehydrate over the following hours, monitor your urine.

Hyponatremia: the hidden danger

Hyponatremia happens when you drink too much water without salts. Sodium in your blood dilutes below critical levels. Symptoms: headache, nausea, confusion, swelling, and in severe cases seizures and coma.

It mainly affects marathoners and triathletes who drink liters during long races. They think they're doing the right thing by drinking tons, but without salts they're poisoning themselves with water.

Prevention: don't drink more than 800 ml per hour during sports, always add salts to drinks for activities over 90 minutes, don't force yourself to drink if you're not thirsty.

Adapt to the season

Summer: increase consumption. Drink 30-50% more. Prefer cooler times (early morning, evening). Wear light and breathable clothing. Always carry extra water.

Winter: even though it's cold, you still sweat (under your clothes). Don't neglect hydration. Drink water at room temperature, not cold.

Mountains/altitude: dry air increases fluid loss through breathing. Drink 20-30% more than usual even if you don't sweat visibly.

For specific sports

Running: carry a water bottle or bottle belt. Plan routes with water fountains. Drink every 2-3 km.

Cycling: two bottles on the bike. One with water, one with sports drink. Alternate.

Gym: 1-liter bottle. Take a sip between sets. Finish the bottle during your hour of training.

Swimming: you sweat even in the pool (you just don't notice in the water). Drink every 20-30 minutes of swimming. Keep a bottle at the pool edge.

Team sports (soccer, basketball): bottles at the sideline. Drink at every break or substitution. Don't wait until the end.

Create your personal hydration plan

Do this test: weigh yourself before a typical workout (60-90 minutes). Drink only when you're thirsty. Weigh yourself after (naked, dry). The difference tells you how much you normally lose. Use this data to plan.

Example: you weigh 70 kg before, 68.5 kg after. You lost 1.5 kg = 1.5 liters. During training you should drink at least 1 liter (to reduce loss to 0.5 kg which is acceptable).

Prepare your sports drinks

Basic recipe for 1 liter: 500 ml water plus 500 ml fruit juice (orange, grapefruit) plus 1/4 teaspoon salt. You get sugars, potassium, sodium. Economical and effective.

Pro recipe: 1 liter water plus 60g maltodextrin (pharmacy/sports shop) plus 1g salt plus lemon juice. Perfect for long races.

Bottles and equipment

Invest in good bottles. For running: bottle belt or hydration backpack (CamelBak). For cycling: two bottle cages on the bike. For gym: 1-liter graduated bottle.

Insulated bottles keep water cool even in summer. Worth the expense. Hot water in summer is unpleasant and you'll drink less.

Monitor your performance

Keep a diary for 2 weeks: how much you drank before/during/after, how you felt, what your performance was like. You'll see the patterns: when you drink well, you perform well. When you drink poorly, you decline.

Use this information to optimize. Every body is different. Find your winning formula.

Combine with food

High-water fruits (watermelon, oranges, grapes) are hydration you can eat. A pre-workout fruit snack helps you start hydrated.

Post-workout: plate of pasta or rice plus vegetables plus salty protein (prosciutto, tuna, cheese). You replenish carbs plus water from food plus electrolytes from salt. Complete recovery.

For races and competitions

Don't experiment on race day. Use the strategy you've tested in training. Race day surprises = disaster.

Bring your own water/sports drink. Don't rely on aid stations if you don't know what they're providing. Check the course beforehand: where are the aid stations, how far apart, are they sufficient.

Listen to your body, but not only

Thirst is a useful but imperfect indicator. Especially in long races, thirst arrives late. Use thirst PLUS fixed timing: drink both when you're thirsty and every 15-20 minutes regardless.

If your stomach rebels (nausea, heaviness), reduce the amount but increase the frequency. Better 100 ml every 10 minutes than 300 ml every 30.

Learn from the professionals

Watch how professional athletes hydrate in your sport. Observe the details: when they drink, how much, what they drink. Copy the strategies, adapt them to yourself.

Read books/articles specific to your sport. Hydration for marathoners is different from hydration for bodybuilders. Specialize.