How Much Water During Exercise?

"Drink more water" is the most-given and least-explained tip in fitness. How much is enough? When is it too much? And do you really need those colorful electrolyte drinks? Here's the honest, simple version.

Losing just about 2% of your body weight in fluid can noticeably drag down performance – focus slips, everything feels heavier. At 75 kg that's only one and a half liters of sweat, which adds up fast on a hot day. At the same time, "drinking liters just in case" isn't the answer either. It's about the right amount, not maximizing.

Before training

Don't walk into a workout already dried out. Drink enough across the day that your urine is pale yellow. Then have a glass (200–300 ml) about 30 minutes before – enough to start well-hydrated without water sloshing in your stomach when you jump.

During training

For a normal session under an hour, a few sips every 15–20 minutes is plenty. You don't need to force a quota – at moderate intensity, thirst is a surprisingly good guide. As things get longer, hotter or sweatier, a bigger gulp now and then is fine.

"If you're thirsty, it's already too late" – true?

You hear this one a lot, and it's only half right. For a perfectly normal session, thirst is a reliable signal – you can follow it without fearing you're already in trouble. It's a bit different for long efforts in serious heat: there, thirst can lag behind, and it's worth drinking regularly before it even shows up. So for most people: thirst is a good compass, and only for extreme sessions do you need a plan on top of it.

After training

Now it's about topping up. A simple method: weigh yourself before and after long, sweaty sessions. For each kilogram lost, drink back about 1–1.5 liters over the next hour or two – slowly and spread out, not all at once. After short sessions, a large glass plus your normal meal usually does it.

Do I need electrolytes?

For a typical gym session or a 30-minute run: no. Water is enough, and you'll easily get the minerals from your next meal. Electrolytes (sodium above all) only get interesting once you're sweating hard for over an hour – long runs, bike rides, exercise in serious heat. Then a pinch of salt in your water or a sugared sports drink helps replace what you lost.

Most people don't need a pricey electrolyte mix – just a water bottle they'll actually carry with them.

Can you drink too much?

Yes, in rare cases. Pouring liters of plain water over several hours can dangerously dilute the sodium in your blood (hyponatremia). This almost only affects extreme endurance athletes who drink "in advance". For everyday training it's a non-issue – but it's why "more is always better" isn't true for water either.

Water, diluted juice or a sports drink?

For 95% of sessions, plain water is the right call – cheap, calorie-free, always on hand. A lightly diluted juice (one part juice, three parts water) adds a little energy and flavor on longer sessions without loading you with sugar. Off-the-shelf sports drinks are often sweeter than necessary: for an hour of lifting they're simply overkill. Save the money and reach for the tap.

The underrated start: mornings

After sleep you're mildly dried out – six or seven hours without a sip leaves a mark. A big glass of water right after you get up sets you straight, long before training is even on the table. Morning exercisers benefit most here: you don't head into your first exercise with a half-empty tank.

How to spot dehydration

• Dark, deep-yellow urine.
• Tiredness or a headache setting in early.
• Cramps toward the end of a session.
• A heart rate that feels "too high" for the effort.