Tennis players cramp because they lose sodium, not just water. A hard summer match can cost 1–2.5 liters of sweat per hour, and sweat sodium runs roughly 500–1,500mg per liter. Water alone doesn't replace that. The fix is sodium plus carbohydrate, started before the first serve and continued at every changeover.
By Sebastian Madlangbayan, state champion and founder of Cleonse.
Why tennis is a hydration problem in a way most sports aren't
I cramped out of a match at 5-4 in the third when I was sixteen. Ninety-something degrees, two and a half hours in, and my legs simply stopped negotiating. I'd been drinking water all day. I remember thinking that was the responsible thing I'd done.
It wasn't. Water was the problem.
Tennis has a structural issue no other sport quite shares:
You can't control the clock. A soccer match ends at 90 minutes. A 5K ends at 5K. A tennis match ends when someone wins, which might be 55 minutes or might be three and a half hours. You cannot plan your fuel around a known duration, so you have to plan around the long version every time.
The work is stop-start but relentless. Points are short and explosive; the accumulated load over three sets is enormous. Your heart rate spikes and drops hundreds of times.
You play in the worst conditions available. Hard courts absorb and radiate heat. Court surface temperature can run substantially hotter than air temperature. There's usually no shade, and you're often on court in the middle of the day because that's when the draw put you.
Your recovery windows are fixed and short. Ninety seconds at a changeover, two minutes at a set break. That's your entire opportunity to take in fluid — you can't sip continuously the way a cyclist can.
Tournaments are multi-day and sometimes multi-match. You might play singles in the morning and doubles at 3pm. What you failed to replace in match one shows up in match two.
Add it up and tennis is a sport where hydration mistakes compound quietly for two hours and then present the bill all at once.
Sodium loss in tennis: the actual numbers
Here's the part that changed how I played.
Sweat rate. During hard play in heat, athletes commonly lose somewhere in the range of 1 to 2.5 liters per hour. Individual variation is large — body size, fitness, heat acclimation, and how hard the points are going all move it.
Sweat sodium concentration. Sweat isn't pure water. Sodium concentration in sweat is typically in the range of 500 to 1,500mg per liter, and this varies enormously between people. It's largely genetic and only partly trainable through heat acclimation.
So the arithmetic: a two-hour match at 1.5 L/hr with moderately salty sweat puts you somewhere around 1,500 to 3,000mg of sodium lost. For a heavy salty sweater in real heat, it can be more.
Now compare that to what you're drinking. A serving of standard sports drink powder carries roughly 150mg of sodium. Water carries zero.
You cannot close a 2,000mg gap with water. And here's the mechanism that turns a deficit into a disaster: when you drink plain water in large volumes while continuing to lose sodium in sweat, you dilute the sodium concentration in your blood further. Your body responds by dumping fluid. You end up peeing out the water you just drank while your sodium deficit deepens.
That's how you can be "drinking constantly" and still cramp at 5-4.
Are you a salty sweater?
Quick field test, no lab needed:
- Dried white streaks or crusty rings on a dark shirt or hat after a match
- Sweat that stings your eyes badly
- A distinctly salty taste when sweat runs to your lips
- A history of cramping late in matches even when you've been drinking
- Sweat that leaves visible residue on your grip or strings
If two or more of those describe you, plan your sodium intake at the high end. If none of them do, you still need sodium — you just have more margin.
When you need electrolytes, and when you need carbs too
These are two different questions and most players conflate them.
Sodium replaces what you sweat out. You need it any time you're sweating meaningfully, regardless of how long you're on court.
Carbohydrate is fuel. You need it when the session is long enough to meaningfully draw down muscle glycogen — and it also helps the fluid get absorbed, because sodium and glucose are co-transported across the intestinal wall and water follows them.
Here's how I'd break it down:
| Session | What you need |
|---|---|
| Under 45 min, mild conditions | Water. That's it. |
| 45–75 min, moderate heat | Water plus sodium. Carbohydrate optional. |
| 75 min+, or any real heat | Sodium plus carbohydrate. Both. |
| Match play, unknown duration | Sodium plus carbohydrate, started before you walk on. |
| Two matches in a day | Sodium plus carbohydrate during both, plus deliberate refueling between. |
| Tournament week | All of the above, plus attention to what you're doing overnight. |
The rule I'd give my sixteen-year-old self: if the match could go three sets, fuel like it will.
This is exactly why I built Cleonse with real sugar in it. A 30g stick is 500mg of sodium, 24g of organic cane sugar, 26g of carbohydrate, 100 calories, and 85+ trace minerals from French grey sea salt. Three ingredients: organic fruit powder, organic cane sugar, French grey sea salt. The sodium replaces sweat losses. The carbohydrate is fuel and helps the fluid absorb. Neither is a compromise — they're the two things a tennis player actually needs on court.
Zero-sugar electrolytes have a real place — I use them on off days and for easy sessions. But a zero-sugar drink during a three-hour match in July is solving half the problem.
The protocol
This is what I actually do. Adjust the numbers to your body, your sweat rate, and your conditions — the structure is the part that transfers.
The day before (tournament play)
- Drink normally throughout the day. Not obsessively — just don't show up already down a liter.
- Salt your dinner. Real food, real salt. Pre-loading sodium the night before a hot match is one of the highest-leverage, lowest-effort things you can do.
- Eat carbohydrate at dinner. You want full glycogen stores at the start line.
- Check the forecast and decide your plan before you're standing in the heat trying to think.
2–3 hours before the match
- ~500ml (about 16–20 oz) of fluid. This gives your body time to absorb what it needs and clear what it doesn't.
- Eat a real meal with carbohydrate. Not a gel, food.
- Check your urine color — pale straw is the target. Clear means you're overdiluting; dark means you're behind.
30 minutes before you walk on
- One Cleonse stick in 16–20 oz of water. 500mg of sodium and 24g of carbohydrate absorbing while you warm up.
- This is the single biggest change I made as a junior. Starting the match already topped up on sodium instead of chasing it from behind is the difference between managing hydration and reacting to it.
- Don't chug it in the last five minutes. Sip it during your warm-up.
During the match
Two bottles courtside:
- Bottle 1: Cleonse. One stick in 16–20 oz.
- Bottle 2: plain water.
At every changeover, drink from both. A few solid pulls of the electrolyte bottle, a few of the water. Don't skip changeovers because you feel fine — feeling fine at 3-2 is not information about how you'll feel at 5-4 in the third.
Practical guide:
- Every changeover from the start, not from when you get thirsty. Thirst is a late signal.
- Roughly a 30g Cleonse stick per hour in real heat, alongside plain water. That's about 500mg of sodium per hour, in the range of typical loss for a moderate sweater in hot conditions.
- Heavy sweater, extreme heat, or a three-set grind? Have a second stick mixed and ready in the bag. A cramp costs you a match; an extra stick costs you a dollar.
- Set break (two minutes)? Take a real drink. That's your longest window until the match ends.
- Watch your grip. Weirdly reliable tell — when your grip starts slipping more than usual, you're usually further into fluid loss than you think.
After the match
- Rehydrate to about 1.5x what you lost. Weigh yourself before and after if you can: every pound lost is roughly 16 oz of fluid to replace. You need more than the deficit because some of what you drink gets excreted.
- A stick in your recovery bottle. Sodium helps you retain the fluid you're drinking instead of passing it straight through, and the carbohydrate starts glycogen replenishment.
- Eat within an hour. Carbohydrate and protein.
- If you play again the same day, this window is the whole ballgame. Everything you fail to replace now, you'll feel in the second match.
Overnight during a tournament
- Salt your dinner again.
- Fluid steadily through the evening, tapering an hour or two before bed so you're not up at 3am.
- Pale straw in the morning means you did it right.
Five mistakes I made so you don't have to
1. Drinking only water. Covered above. It's the single most common cramping cause in junior tennis and it feels responsible while you're doing it.
2. Waiting for thirst. Thirst lags actual fluid deficit. By the time you're thirsty on a hot court you're already behind, and once you're behind mid-match you generally stay behind — your gut can only absorb so fast.
3. Skipping the pre-match stick. Trying to catch up on sodium during a match is a losing race against your own sweat rate. Start ahead.
4. Chugging at changeovers. A large volume at once sits in your stomach and sloshes. Steady, consistent intake at every changeover beats a panicked 20 oz at 4-4.
5. Treating a doubles match as a rest day. You're on court, in the sun, sweating, for another hour or more. Fuel it.
Why three ingredients matters for a competitive player
Two reasons, both practical rather than philosophical.
GI tolerance. Junior and college players talk about stomach issues constantly — heaviness, sloshing, nausea in the third set. Every extra additive is another variable. Gums, sugar alcohols, high-intensity sweeteners, and bulking carbohydrates like maltodextrin all give some people trouble under exertion. A drink that's fruit powder, cane sugar, and salt is about as simple as it gets to test and to tolerate.
You'll actually finish it. This is underrated. Stevia has a lingering finish that builds the longer you drink, and a lot of players quietly stop drinking their electrolyte bottle midway through a match because it stopped tasting good. The best hydration protocol is the one you complete. Cleonse tastes like lemonade or strawberry lemonade — no aftertaste, not overly salty — which means the bottle is empty at the end of the match instead of two-thirds full.
For anyone who competes under a governing body: check your organization's supplement rules yourself. A three-ingredient organic food product is about as low-risk as this category gets, but verifying is your job, not a marketing claim I'm going to make for you.
One-page summary
- Tennis players cramp from sodium loss, not just fluid loss. Water alone can make it worse.
- You lose roughly 1–2.5 L of sweat per hour in hard summer play, at 500–1,500mg sodium per liter.
- Start ahead: one stick 30 minutes before you walk on.
- Two bottles courtside: electrolytes and plain water. Drink both at every changeover.
- Roughly one stick per hour in heat; more if you're a salty sweater.
- Carbohydrate isn't optional for long matches — it's fuel, and it helps fluid absorb.
- Rehydrate to ~1.5x your loss after, especially if you play again that day.
- Salt your dinner the night before hot matches.
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Shop CleonseFrequently asked questions
How much water should a tennis player drink during a match?
Aim to drink at every changeover rather than to a fixed total. A practical target in hot conditions is roughly 16–32 oz per hour split between an electrolyte drink and plain water, adjusted to your sweat rate. Weighing yourself before and after a match tells you how close you got — every pound lost is about 16 oz of fluid.
Why do tennis players cramp even when they drink a lot of water?
Because cramping in hot, long matches is closely associated with sodium loss, and water doesn't replace sodium. Drinking large volumes of plain water while continuing to sweat can dilute blood sodium further, prompting your body to excrete fluid rather than retain it. Sodium alongside the fluid is what keeps you in balance.
Should tennis players drink electrolytes with sugar?
For matches and long practices, yes. Carbohydrate is your primary fuel during sustained effort, and sodium and glucose are co-transported across the intestinal wall, which supports fluid absorption. For short, easy sessions, water or a zero-sugar option is fine. Cleonse pairs 500mg of sodium with 24g of organic cane sugar for exactly this use case.
When should I take electrolytes before a tennis match?
About 30 minutes before you walk on court, mixed into 16–20 oz of water and sipped through your warm-up. Starting the match with sodium already on board beats trying to catch up mid-match, when your absorption rate becomes the limiting factor.
How do I know if I'm a salty sweater?
Look for white streaks or crusty residue on dark clothing and hats after training, sweat that stings your eyes, a strongly salty taste when sweat reaches your lips, and a history of late-match cramping despite drinking. If several of those apply, plan your sodium intake toward the high end of the range.
What should I drink between two matches in one day?
Start immediately after match one: fluid with sodium plus carbohydrate, targeting roughly 1.5x the weight you lost, and real food within the hour. The gap between matches is the only recovery window you get, and whatever you don't replace shows up in the second match.
Sebastian Madlangbayan is a state champion tennis player and the founder of Cleonse, a 3-ingredient organic electrolyte drink mix — organic fruit powder, organic cane sugar, and French grey sea salt, with 500mg of sodium and 85+ trace minerals per stick. This guide reflects personal competitive experience and general sports-nutrition principles. It is not medical advice; if you have a medical condition or take medication affecting fluid or sodium balance, talk to a qualified professional before changing your intake.
Editor's note: sweat rate and sweat sodium figures cited here are general ranges widely reported in sports-nutrition literature and vary substantially between individuals; they are offered as planning guidance, not as measurements of any specific athlete. Product figures are from the Cleonse label.