Cramping & Endurance Sports – Why Does It Happen and How to Address It

Why Marathon Runners Cramp — And What You Can Do About It

 

If you’ve ever had a muscle cramp in the middle of a marathon — or worse, in the final
stretch when you’re almost there — you know how frustrating it can be. You hydrate,
you take your salt tabs, you do everything “right”… and your leg still locks up.
A recent study called “Muscle Cramping in the Marathon: Dehydration and
Electrolyte Depletion vs. Muscle Damage” by Martínez-Navarro et al gives us some
new insight into what’s really happening when marathoners cramp. And spoiler alert —
it’s probably not just about electrolytes.

 

What the Study Looked At

Researchers followed nearly 100 marathon runners, measuring things like hydration,
electrolyte levels, and signs of muscle damage before and after the race. About one in
four runners experienced cramping during or after the marathon.

When they compared the “crampers” to the “non-crampers,” something interesting
showed up:

• Hydration and electrolytes were about the same in both groups.
• Markers of muscle damage (think: creatine kinase, a chemical that leaks out when
  your muscles get stressed) were much higher in the runners who cramped.

In other words — it’s not always about running out of water or salt. It’s more about how
tired and overworked your muscles get during the race. When muscles are pushed
past their limit, they lose some of their normal control, and that’s when cramping can
strike.

So What’s Really Causing Those Cramps?

Cramping in long races seems to be a sign that your muscles are simply overworked
and overstressed — especially in the later miles. When a muscle is pushed past its
limit, it can lose some of its normal “communication” with the nervous system. The
result? Those painful, involuntary contractions that can stop you in your tracks.
The study also noticed that runners who cramped were less likely to include strength
training in their preparation, and they tended to slow down more in the later stages of
the race — another clue that fatigue plays a major role.

What This Means for You

Here’s how I’d break it down:

• Cramping isn’t just about fluids and electrolytes. Yes, stay hydrated and use
  a balanced race-day nutrition plan — but don’t rely on salt tabs alone to save
  you.
• Your muscles need to be trained to handle fatigue. Think of it like preparing
  your body to “stay strong” even in the last few miles, when things start to fall
  apart.
• Strength training helps. Building stronger, more resilient muscles reduces
  stress and helps them maintain control under fatigue.

Five Ways to Keep Cramps Away

Here’s how you can train smarter and help your muscles go the distance:

1. Get Stronger

   You don’t need fancy equipment or hours in the gym. Just one or two short strength
   sessions a week can make a big difference.

   Try: squats, lunges, calf raises, bridges, and planks. Strong muscles handle the pounding of long miles much better.

2. Practice Running on Tired Legs

   Every once in a while, add a few strides or short bursts at the end of your long run. This
   teaches your muscles to perform when they’re already fatigued — just like they will late
   in the race.

3. Pace Yourself Early

   Many cramps happen after mile 16–18 because the early miles were too fast. Start a
   little slower than you feel you should. You’ll thank yourself later when you’re still running
   strong.

4. Hydrate Smart — But Don’t Overdo It

   Drink regularly and use a balanced sports drink or electrolyte mix. But remember, too
   much plain water can actually throw things off. Keep it balanced and consistent. But
   remember, this won’t fix cramping if your muscles aren’t prepared.

5. Recover Like a Pro

   Foam roll, stretch, sleep, eat well, and take easy days seriously. Your muscles need
   recovery to rebuild and adapt between workouts.

The Bottom Line

Marathon cramps aren’t just a hydration problem — they’re a muscle preparation
problem. Cramping isn’t a sign that you have failed, it’s a sign that your muscles have
hit their limit. The more you train them to handle fatigue, the less likely they’ll be to
revolt on race day.

So, yes — keep your fluids and salt in check, but make sure you’re also building
strength, training smart, and pacing wisely. Your muscles will thank you at mile 24!