😖 Muscle Cramps in Ironman: What 30 Years of Data Tell Us
Muscle cramps have haunted endurance athletes forever. I personally have been very fortunate to not ever have a race-wrecking cramp during an event (though I’ve had my share of adductor doozies getting changed in my car once the race was done!). But I know many athletes who have tried to solve what felt like a medical mystery for years: sucking down salt tablets, guzzling electrolytes, even carrying pickles or McDonald’s mustard packets in their pockets to employ at the first sign of a twitch.
Many racers focus on electrolytes especially, which makes sense when you consider that electrolytes (i.e., sodium, potassium, magnesium) along with hydration still play vital roles in muscle function. But a new look at three decades of data from the IRONMAN World Championship, which has historically been held on the hot, humid Big Island of Hawaii, challenges some long-held assumptions and reinforces others.
Researchers reviewed more than 10,000 medical encounters from nearly 50,000 Ironman competitors between 1989 and 2019, focusing on athletes treated for exercise-associated muscle cramps (EAMC). The headline finding? Electrolytes didn’t appear to be the main issue.
Athletes who cramped had similar blood sodium and potassium levels as those who didn’t. Cramps were also equally common in women and men. That’s a strong strike against the idea that cramps are primarily driven by salt loss or electrolyte imbalance–an explanation that’s been steadily losing scientific support for years.
What was associated with cramping? Athletes who cramped were more likely to show signs of exhaustion, hypotension (low blood pressure), headaches, abdominal pain, and dehydration, which the researchers determined primarily through body weight loss measured during an event. A prior history of cramping also strongly predicted future cramps.
So, we’re back to saying dehydration causes cramps? Not necessarily (though it’s likely working in the background). The current medical consensus points primarily to premature local muscle fatigue and altered spinal neuromuscular control, which is a fancy way of saying the muscle has done more work than it was prepared for, and the nervous system loses the signal that tells it to relax. Previous cramping, high intensity/overpacing, and prior injury are widely considered major risk factors.
These latest findings don’t necessarily contradict that model. They likely describe the same problem from a different angle. Weight loss in a race (what the researchers here framed as dehydration) often reflects a mix of glycogen depletion, underfueling, heat strain, GI issues, and overall physiological stress. All of those factors can lower a muscle’s fatigue threshold. So, “dehydration” may be a marker of total system overload, which would be where your neuromuscular control starts to unravel.
What does this mean for endurance athletes?
You certainly want to take care of your basic fueling and hydration needs. By taking in adequate carbs and fluids, you can limit overall strain. Sodium can help support hydration and fluid retention, and, of course, is especially important in the heat, particularly if you’re a salty sweater, but chasing electrolytes alone isn’t necessarily going to cure your cramps. If you’re a cramper, that means you’re vulnerable to cramping (which, you likely already know!). That means targeting that vulnerability with a multifactorial approach:
Practice training specificity and pacing, so your muscles are prepared for the tasks they’ll be asked to perform in the environment you’ll be performing in. Heat adaptation and/or acclimation can help reduce heat strain.
Resistance training is also a plausible way to reduce your risk of cramping by improving strength and delaying local fatigue. Over the years, I’ve known mountain bike racers who successfully solved their cramping issues with dedicated strength training. So it’s definitely worth a shot if you aren’t already.
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