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There are few more frustrating aflictions during a race than cramp. You know the feeling - you’re striding along, in a good rhythm, when all of a sudden - out of nowhere - your calf/quad/hammie or even the arch of your foot suddenly goes into spasm. And it’s all you can do to stay upright, let alone keep running.

But what causes cramp, and how can we avoid it? An email from Precision Fuel & Hydration sent me down the rabbit hole on the subject of cramps this week and the TL;DR version is: it’s complex, and individual. So there’s no magic pill - literal or metaphorical.

While cramping is common, it turns out exercise associatied muscle cramps, the sort runners are prone to, are wickedly difficult to study. They are unpredictable and hard to replicate, and therefore observe, in laboratory conditions.

And because the stakes are relatively low - no-one dies from a cramping hamstring - the field doesn’t attract much research money, and therefore attention. Given all this, it’s unsurprising the studies that have been done often turn up contradictory findings.

Sometimes hot weather is a factor, other times it’s cold weather. Some studies point to dehydration, others rule it out. One review of the studies points out there are “mutually contradictory” findings across research, and sometimes there are even contradictory findings in the same study!

Another review pointed out the “quality of experimental methodology varies considerably” across studies. Having said all that, there are two main theories about what causes cramps: the dehydration/electrolyte depletion theory and the altered neuromuscular control theory.

In recent years, the dehydration/electrolyte depletion theory has lost ground. This theory proposes that when you sweat, you lose both water and electrolytes - predominantly sodium.

This is a problem because, as the body tries to shift its remaining sodium to where it’s needed most, fluid moves from the cells to the “interstitial” spaces in the body. This in turn puts pressure on nerve endings and cramp is the end result. Or so the theory goes.

There is lots of anecdotal evidence to back this. The problem is, it’s proved difficult to gather the evidence to support it. That’s partly for the reasons above - cramps are hard to predict or replicate and there are a number of variables in play at any one time.

Some data points that have been cited in studies also suggest the theory doesn’t hold water, if you’ll excuse the pun. One of the most recent was published in January. Exercise-Associated Muscle Cramps in Ironman-Distance Triathletes Over 3 Decades was an enormous study, looking at almost 50,000 Ironman Triathlon competitors between 1989 and 2019.

This found no material difference in sodium levels in the blood of the crampers versus the non-crampers. On the surface, this suggests a sodium deficit can’t be blamed for the cramping. This has been seen as a significant argument against the dehydration/electrolyte depletion theory.

But the people at Precision argue just looking at blood sodium levels gives only half the picture. When your body loses sodium, the last place to be depleted is your blood, because maintaining a sodium balance in blood is vital.

This means when you sweat, you’re losing sodium from elsewhere - including the fluid surrounding your muscles. And it’s this sodium imbalance, the Precision people argue, that causes cramping. Makes sense to me.

That mega-study also found a strong correlation between dehydration and the crampers. This runs counter to other studies that have found no such correlation. This finding adds some weight to the dehydration/electrolyte depletion theory.

Work hard, cramp hard

The altered neuromuscular control theory proposes that cramping is caused by muscle fatigue. As we fatigue, the signals travelling from our brains to our muscles via the nervous system get scrambled, and this leads to cramping.

This gets quite technical, involving Golgi tendon organs, muscle spindles and motor nerves, but essentially what’s been observed is that as muscles fatigue, the signals telling a muscle to contract are “excited”, while those telling it to relax are “inhibited”. Which is a recipe for a cramp.

What all this means is pushing too hard is likely to cause cramps. Again, there is plenty of anecdotal evidence to back this. Cramps often occur late in races. They are also more prevalent in people who have under-prepared for big events.

Again, this is hard to definitively prove or disprove, but it can be tested more readily in a lab by using electrical stimuli to bring cramps on, and observe what happens. The fact that stretching a cramp usually provides immediate relief is also seen as evidence that this theory is on the money.

What’s beginning to emerge, perhaps because of the lack of hard evidence either way, is the view that both theories are playing a part, and they impact different people in different ways.

What’s to be done?

Thankfully, there are practical steps you can take to reduce the chances of cramping - even though we can’t be sure exactly what causes it.

Firstly, on the dehydration/electrolyte front, it’s easy and relatively cheap to have a sweat test done. This will calculate the amount of sodium you lose per litre of sweat. Essentially, it will tell you definitively how “salty” a sweater you are.

If you combine this with a sweat volume test, which is easy enough to do yourself, you can then create a race/long run plan that will ensure you are taking in enough electrolytes on every run to compensate for what you’re losing in sweat.

(I wrote a three-part series on this earlier in the year, focused on dehydration rather than cramps, and I’ve linked to those pieces at the bottom of this column.)

Staving off neuromuscular control issues takes less planning, but more will power. The prevailing knowledge on this front is that you need to resist the temptation to push too hard, too early in a race.

Training is the other key element. Putting the miles in on the training track will push back the point where muscles fatigue. But it’s got to be done in a gradual, managed way.

My take (FWIW)…

One of the key findings of the 30-year Ironman Triathlon study is that the number of people reporting cramps fell dramatically. This correlates with Precision’s own cramping survey.

Over the 10 years it’s been running, the percentage of people reporting issues has fallen from 95 per cent to around 75 per cent. Given it’s a survey about cramping, it’s no surprise the figures are so high.

The survey also found salty sweaters are more prone to cramping. This would support the dehydration/electrolyte depletion theory. While this is self-reported, so not bullet-proof from a methodological perspective, it is still interesting.

Unsurprisingly, more than 60 per cent of the 500 or so respondents to the survey said their cramps came towards the end of races. At a point where fatigue and dehydration/electrolyte depletion would be present.

For my part, I know I am both a salty and a heavy sweater, so on every run I lose more sodium than your average Joe. But while I’m no stranger to cramps, I’m certainly not plagued by them. This gives me pause for thought re the dehydration/electrolyte depletion theory.

However, what I do know for sure is that I feel a damn sight better after a race if I’ve rehydrated and taken on board electrolytes, regardless of cramping. So that’s a practice I will continue.

In the final analysis, it makes sense to cover all bases. Book a sweat test, run your own sweat volume test, calculate your sodium loss rate, pace yourself and don’t skimp on the training.

Do all that, and you’ll put yourself in the best possible position to finish your next ultra cramp free.

The sweat series

• How to get the most out of a sweaty business

• The science of sweat

• Planning for success, one sip at a time

Upcoming Events

There are way too many events for me to list everything that’s happening around the country, but here is a selection of upcoming races (with a bias towards South East Queensland).

The Running Calendar website is a great source if you want a comprehensive understanding of what’s available around the country.