sweatsciences
CrossFit hydration & electrolytes

You leave a puddle — so you drink. The salt is what you miss.

Unlike a bike ride, CrossFit leaves you visibly wrecked, so most people do drink enough water. The mistake is more specific: in a hot box, an intense hour flushes out real sodium, and plain water or a light drink puts back a fraction of it. The cramp on the last round and the flat feeling that evening are usually a sodium gap, not a fluid one.

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Why the fix is sodium, not more water.

Sweat sodium varies about tenfold between athletes — roughly 200 to 2,000 mg per litre. A hard, hot session drives a high sweat rate, so a salty sweater can lose more sodium in an hour than they'd guess, while the standard advice ("hydrate!") only ever means water. Chugging more plain water on top of a heavy sweat can even work against you — it dilutes the sodium you have left. The move is to put the right amount of sodium back, matched to how you actually sweat.

The tell. If you drink plenty and still cramp, still feel wiped, still get the headache — that's the signature of replacing water but not salt. Here's why that happens →

The protocol around a WOD.

BeforeArrive hydrated with sodium on board. A measured dose in ~16 oz beforehand beats trying to catch up after a metcon flattens you.
DuringSip between efforts if the session allows — you're topping up, not drinking through it.
AfterReplace to your number. Your calculated sodium, potassium and magnesium in water over the next hour — this is where most of it goes back.
Double-daysTake it seriously between sessions. Two hard sessions in a hot box compound the loss; the recovery drink is the training here.
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Keep reading

Measure it

Your sweat rate

Weigh in before and after a hard session — your real hourly loss, no wearable.
The race format

HYROX

The 60–90 minute hybrid version — same sodium-first logic, longer.
The receipts

Every product, mg by mg

What your current tab delivers, and the cheap way to hit your number.