Exercise-associated muscle cramp (EAMC). That sudden, brutal seizing of a muscle that can turn a great race into a hobbling death march in a matter of seconds. If you've experienced it mid- or post-race, you'll know exactly what I mean.
At PF&H, our co-founder Andy's own struggles with cramp early in his athlete career led him to founding Precision Fuel & Hydration in a bid to help athletes avoid the same issues that hindered his performances as a young triathlete.
So, we're always interested when new research helps further our understanding of this race ruining condition. Paal Nilssen and colleagues published the largest real-world dataset on cramping in endurance sport in 2026, and some of its findings challenge what many experts have been saying for the past decade...
5 takeaways from the study
Researchers from Washington State University analysed records from the IRONMAN® World Championship medical tent in Kona, Hawaii, spanning 30 years of racing from 1989 to 2019. It included 49,530 race participants and 10,533 medical records!
Crucially, this isn't a survey where athletes reported their cramps retrospectively. These are records from physicians who treated athletes presenting at the medical tent, including actual blood tests, weight measurements, and clinical diagnoses. In other words: real data from real athletes in real distress.
The authors aimed to observe any differences between the athletes presenting at the medical tent with and without exercise-associated muscle cramp and then to explore whether prior EAMC during the same race increases the risk of subsequent cramping episodes.
1. Cramping dropped by 80% over 30 years
In 1989, 12.8% of athletes sought medical treatment for cramps. By 2019, that number had fallen to just 2.6%. It's worth noting that these figures only reflect athletes who sought medical attention, so the overall incidence of cramping will likely be higher in both years, but this is still a dramatic decrease.
The researchers suggest that improved hydration education and better race-day strategies are likely contributors. We'd tend to agree. The fact that cramping rates have fallen so substantially over a period of time when endurance athletes have become far more educated about hydration is encouraging, and it suggests that what you do in the lead-up to and during a race genuinely matters.
2. Dehydration was strongly associated with cramping
This is the finding that directly contradicts some of the loudest voices in sports science over the past ten years or so. And it starts to help us understand the influence of sweat and, therefore, sodium losses on the wider picture of cramp risk.
Cramping athletes lost significantly more weight during the race than non-cramping athletes. Weight loss during exercise is widely used as a marker of dehydration, and the cramping group was measurably more dehydrated at the point of medical assessment.
The researchers themselves acknowledge this sits at odds with several well-cited studies, including a prominent 2011 paper on Kona athletes that concluded dehydration was not a risk factor. The difference here is scale: 2,863 cramping cases over three decades the latest study, versus a few hundred participants in a single-year study in 2011.
It's certainly worth noting what this study could not measure: individual sweat sodium concentration and net sodium losses, fluid intake, sweat rate, and total fluid loss during the race.
The practical implication is straightforward: staying on top of your fluid intake during long events isn't just about performance. It may genuinely help you avoid the kind of physical collapse that ends races.
3. Crampers had identical sodium levels to non-crampers
The study also found that cramping athletes had virtually identical blood sodium and potassium levels to non-cramping athletes at the point of medical treatment. There was no association between severe low sodium (hyponatremia) and muscle cramping either.
For many researchers, this has been the nail in the coffin for the electrolyte hypothesis of cramp. If low blood sodium causes cramping, you'd expect cramping athletes to have lower sodium levels, but they don't.
But here's the important nuance, and it's something we've been saying for years: blood sodium levels aren't a proxy for total body sodium status.
Your body tightly regulates the sodium concentration in your blood because getting it wrong is genuinely life-threatening. So when you lose large amounts of sodium through sweat, your body pulls sodium from other compartments, including the fluid that surrounds your muscles, to keep blood levels stable. The blood test can look perfectly normal even when your total body sodium stores, and your muscles and cells (intracellular hydration status) are significantly depleted and dehydrated.
So, the finding that blood sodium isn't different between cramping and non-cramping athletes doesn't mean sodium is irrelevant. It means a blood test isn't the right tool to measure what's happening in the muscles during the race. You can read more about why sodium matters for athletes here.
4. Pushing hard dramatically increases your cramp risk
Athletes who cramped had significantly faster finishing times and arrived at the medical tent earlier in the race. In other words, the people cramping tended to be the ones going fastest.
This aligns with the most widely supported theory of exercise-associated cramp: the neuromuscular fatigue hypothesis. The idea is that when muscles are pushed towards their limits, the balance of nerve signalling that tells a muscle to contract and relax gets so disrupted that the muscle gets stuck in a state of involuntary contraction.
This is why cramping is so common in the latter stages of races, and why it disproportionately hits athletes who are going harder than their volume and intensity of training have prepared them for. Pacing matters, as does maintaining a decent hydration status, and the two interact: a dehydrated, fatigued muscle is probably more susceptible to the neuromuscular failure that triggers cramping than one in isolation.
5. If you cramped once, you'll likely cramp again
The strongest predictor of repeat cramping in this study was having cramped earlier in the same race. Athletes who had already been treated for cramp were 2.4 times more likely to return to the medical tent with cramping again.
This makes physiological sense: once the conditions that trigger cramping are present, whether that's fatigue, dehydration, or both, they don't simply disappear after one cramp episode resolves. If anything, they worsen as the race continues. This is a strong argument for taking cramping seriously early in a race, rather than pushing hard early on and hoping for the best.
Cramping also came alongside other symptoms related to fatigue and dehydration: athletes presenting with cramps were more likely to have exhaustion, low blood pressure, nausea, and headaches. These aren't isolated events. They are signs that the body is under significant overall physiological stress.
What does this mean for you?
Cramp is multifactorial. This research doesn't point to a single silver bullet, but it does give us a clearer picture of the risk factors, and most of them are manageable.
Hydration and sodium
Staying well-hydrated throughout long events reduces any extra fatigue associated with getting dehydrated and, based on this evidence, reduces your cramping risk too. But drinking enough fluid to limit body mass loss with just water isn't the whole story. Your sweat contains significant quantities of sodium, and simply drinking plain water doesn't replace that lost sodium.
Since everyone loses a different amount of sodium in their sweat, and especially if you're prone to cramping, replacing a decent proportion of your sweat sodium losses is important in endurance events. A Sweat Test can give you a precise picture of this by telling you how much sodium you lose per litre of sweat.
Before long or particularly hot events, consider preloading with PH 1500 electrolytes in the hours before the start. The higher sodium concentration helps you retain more fluid and start the race in a well-hydrated state, which gives you a meaningful buffer before dehydration starts to accumulate.
Pacing and training
The data is clear that harder efforts are associated with cramping. That doesn't mean you shouldn't push hard, but it does mean your pacing strategy needs to be dialled. Making your training specific to the intensity, duration and course profile of your event helps your neuromuscular system adapt to the demands it's going to be under, better preparing it to handle the race.
Know your history
If you've cramped in a race before, take that seriously in your preparation. This study confirms what most coaches and athletes already suspected: your personal cramping history is one of the best predictors of future cramping. Plan your hydration and pacing accordingly, rather than hoping this time will be different.
Reflect on your training, pacing and hydration strategies leading into and during that race. Adjust appropriately by making your training more specific, refine your pacing targets and adjust your fluid and sodium intake to better meet your needs.
What does this mean for the cramp debate?
This study doesn't resolve the cramp debate entirely, but it adds important real-world weight to a picture that is becoming clearer: cramp is multifactorial and is not caused by either neuromuscular fatigue OR dehydration, but rather a combination of the two. Electrolyte blood levels during a race aren't a reliable indicator of hydration status across the whole body, and certainly not at the level of the muscle. The fact that blood sodium levels look normal in cramping athletes doesn't mean sodium is irrelevant to the process.
The 80% decline in cramping rates at Kona over 30 years is, in our view, genuinely encouraging. It suggests that education, better preparation, and improved hydration strategies really do work. If you're a regular cramper, there is hope, and there are practical steps you can take.
If you want to refine your own hydration strategy, you can build a free personalised Fuel & Hydration Plan or read more about why cramp happens and what to do about it.
