- Cramp isn't just a hydration problem. Muscle fatigue plays a big part too.
- Electrolytes matter, but they're not the whole story.
- Two approaches: reactive (stop a cramp that's already starting) and preventive (build your baseline so it doesn't).
- What works varies by runner. Test it in training, not on race day.
"Drink more water and add some salt." That's the advice most runners get told when they cramp, and it's been repeated so often it's basically folklore at this point. Sometimes it works. Often it doesn't, and you're left wondering why you did everything right and still seized up at kilometre 35 anyway.
It's not just what you're drinking
Electrolytes genuinely matter. Sodium, magnesium, potassium, all play a part in how your muscles contract and let go again. But there's another factor that gets less airtime: plain old fatigue.
A muscle that's been working hard for hours gets twitchy. The signals telling it to contract and relax start misfiring the more tired it gets, hydration status aside. Which is a fairly annoying design flaw in the human body, but here we are.
This is also why cramp tends to turn up late in a race rather than early. Early on you're usually still well hydrated. Late on, your legs are just tired, and tired muscles cramp more, water bottle or not.
Two different problems, two different fixes
There's an electrolyte side and a fatigue side to this, which means there are two ways to deal with it.
Reactive is what you reach for once a cramp is already threatening. Something like 32Gi Cramp Assalt, which works more on the neuromuscular side than simply topping up salt.
Preventive is the boring, unglamorous stuff you do beforehand. Regular electrolyte use in the lead-up with something like REVIVE Daily Electrolytes or SaltWTR, building a baseline so the reactive stuff has less work to do on the day.
Neither one is the "correct" answer on its own. Most runners are better off with both in the kit rather than betting everything on one.
Why the same fix doesn't work for everyone
Some runners cramp and a straightforward electrolyte top-up sorts them right out. Others do everything by the book and still cramp, because their issue is more on the fatigue side, and no amount of salt was ever going to fix that.
Worth figuring out which camp you're in before race day, not during it. Test things on a long training run when the only thing at stake is your Saturday morning, not your race. Our Race Day Fuelling guide covers how to build that testing into your training block.
So what helps?
Cramp is more complicated than "you didn't drink enough." Work out what's actually driving yours, sort a preventive routine for the weeks before, and keep something reactive on hand for when it happens anyway. Because it probably will, at some point, to all of us.
Still not sure where to start? Try the Fuelling Diagnostic for a plan built around what you're actually doing.
Does drinking more water stop cramp?
Sometimes, but not always. Cramp is often linked to muscle fatigue as much as hydration, so water alone doesn't fix it for everyone.
Why do I cramp late in a race but not early on?
Fatigue builds through a long effort, and tired muscles cramp more easily regardless of hydration. That's why it tends to hit in the closing stages rather than the first half.
What's the difference between a reactive and a preventive approach to cramp?
Reactive is something you use once a cramp is already starting, aimed at the neuromuscular side. Preventive is regular use beforehand to build your baseline electrolytes, so you need the reactive option less often.
Should I test cramp products before race day?
Yes. Everyone responds differently. Work it out in training, not mid-race when it actually matters.
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