Cramping My Style: Exercise-Associated Muscle Cramping in Running

Why we cramp while running and what we can do about it.

By on July 9, 2013 | Comments

Stay the CourseCramping sucks. I know, from experience, dude.

Cramping, or more specifically, exercise-associated muscle cramping (EAMC), is as much a part of the ultra experience as GU and handhelds. Yet, it is remarkable how little The Communities – both the scientific and ultra – truly know about cramping.

I wish I’d known more. I thought I did. But sometimes knowing what we do not know is nearly as good.

In order to clear the air, and clean the slate, I’d like to review some old concepts, introduce some new ones and try to put forth practical, evidence-based troubleshooting plan if and when cramps threaten to derail your ultra experience.

The Origins of the Cramp & Salt Myth

It’s funny how often a small, inconsequential event can snowball into dogmatic law.

If you were to poll a hundred ultramarathon runners, the vast majority of respondents would claim that muscle cramps were due to “an electrolyte imbalance” or a deficiency in sodium, potassium, or other elements. The belief pervades beyond the trails: I can only smile and nod politely when my patients tell me they combat their night cramps by “eating more bananas,” implying that a potassium deficit somehow causes their cramps.

It does not.

We don’t know much about EAMC, but what we do know, definitively, is this: There is no association between blood (or sweat, or urine) sodium concentrations – or hydration status – and muscle cramps.

None. Zero.

Tim Noakes, MD, devoted 429 pages in his 2012 work, Waterlogged, to the effort of disposing that myth. I, too, did my part, with a good ten-thousand words in this column a year ago. Yet, the presence of S!Caps, Salt Stick, table salt and other supplements in ultrarunner’s pockets hasn’t diminished in the slightest.

Why? There several reasons, beginning with a miniscule but impactful study nearly a hundred years ago. Then, it was the Gatorade revolution. On top of that, mounds of anecdotal evidence: runners implicitly know that salt helps.

And you know what? It does work. We know that, with scientific evidence to boot. But why it helps is not why you think.

Exercise-Associated Muscle Cramping – What We Know

In Waterlogged, Noakes provides historic context to our belief of a salt and cramping association.

The belief in the association between cramping and sodium deficit came from a study nearly a hundred years ago, involving British mine workers. Mine owners and scientists were curious about the cause of muscle cramping in miners, so they conducted a study examining cramping miners and the sodium content of their body secretions: sweat and urine. Based on this single study, the belief that cramps were caused by low sodium was born. And, in the 1960s, scientists jumped on this nugget and ran with it.

The study was tragically flawed: insufficient subjects, a lack of controls, and – most outrageously – completely failed to show any correlation between cramping and sodium. Instead, they found a single subject with low sodium in his urine. That’s it. Thus, our belief of salt and cramping originated from a urine sodium sample of a single study, of a single miner… who did not even experience muscle cramping!

This finding lay dormant, until the 1960s. The history of Gatorade and performance is well-documented in Waterlogged, and described in detail in last August’s column. Because of several confounding factors (ad libitum hydration, sugar intake, and placebo effect, to name a few), the belief that salt benefits performance ran roughshod through the athletic community.

Today, that belief is nearly unshakable.

However, since then, all subsequent studies of sodium concentrations – in blood, muscle tissue, and urine – failed to show any association between cramping and sodium levels.

Noakes reviews the literature, and outlines the current research:

  • There is not a single study that shows blood electrolyte concentrations – including sodium – are abnormal at times of muscle cramping. On the contrary, four recent studies (1984-2009) have shown that cramping athletes have completely normal blood sodium levels.
  • There is not a single study that demonstrates dehydration to be a factor in cramping: in fact, the same aforementioned studies noted that cramping athletes are no more dehydrated than controls.
  • There is no evidence that body temperature of exercising athletes has any effect – that cramping athletes have higher core temperatures – on cramping during endurance activities. In fact, studies on swimmers demonstrate cramping can occur in extreme cold water conditions.
  • One body of studies that did find that “salty sweaters” experienced more cramps (Bergerson, 1996, 2003; Stofan, Zachwieja et al 2005), but these studies failed to have adequate control groups, and they failed to measure blood or sweat sodium concentrations at the time of cramping. Interestingly, one particular finding from these studies found that crampers had higher dietary sodium intakes, and that they sweated higher concentrations of sodium – opposite of the author’s conclusions.
  • When cramping occurs in people with medical conditions (such as hyponatremia), the cramps are generalized throughout the body, affecting multiple groups. In contrast, exercise-induced cramping invariably affects only specific groups involved in repetitive contractions. Therefore, it is unclear as to how a general body or blood sodium deficiency could cause cramping localized only to specific groups.

So, we may not know exactly what causes cramping, but we know what does not cause cramping: low blood or muscle sodium content does not affect cramping.

But… before you un-bookmark from your browser, and cancel your order of “Stay the Course” trucker hats and racing bun huggers (release date, TBD) hang on:

There is evidence that salt helps us in racing. But it’s not why you think. Hang in there.

What We Think We Know: Cramping & the Altered Neuromuscular Control Theory

Noakes and his colleague, Dr Martin Schwellnus (1997) have proposed another theory to explain EAMC, where a reflex – found somewhere in the muscle or nervous system – that normally balance muscle contractions, fatigues. Because of that fatigue, the exercising muscle becomes too excited and begins to cramp.

In a recent podcast interview with Trail Runner Nation, Noakes elaborates:

[Dr. Martin] Schwellnus developed the theory that there are reflexes in the muscle that prevent them from cramping…. When we run, and, in particular, when we run slightly faster than we want to (or that we really should be running), it seems that that reflex gets tired, and the inhibitory reflexes become less strong. And as a consequence, the excitatory impulses… become dominant. And as a consequence, the muscle goes into cramp.

And we know that, because if we look at the electrical activity in the muscles, we notice that before they cramp, the activity starts to rise. So something’s changing in the muscle, that’s making it more prone to going into cramp. And then, you continue for a bit further, and it goes into a full cramp.

And the point is, it is an electrical phenomenon, a reflex, that may originate in the brain (or more likely originates in the spinal cord), but has almost certainly got nothing to do with dehydration or sodium balance, and has almost everything to do with genetic predisposition and also has got everything to do with how tired you are, and how hard you’ve exercised.

Noakes adds,

The remedy, unfortunately, is to do lots of stretching to the [affected] muscle, lengthening the muscle, because what we have also found, is that, muscles that haven’t been lengthened – muscles that have been working in a small arc, and working in a shortened position – those are the muscles that are going to cramp. So you need to stretch the muscle, lengthen it, to make it less susceptible to cramping.

Several studies have helped to confirm this nerve-plus-muscle mechanism for cramping. (Norris, Gasteiger et al. 1957; Minetto, Botter, et al. 2008; Stone, Edwards et al. 2003) In these studies, cramps were induced by stimulating certain muscles, and cramps were abated by stimulating other muscles – reinforcing the notion of a balance between motor firing occurs in a non-cramped state, and that this is disrupted with prolonged, fatiguing activity.

Who Cramps & Why

More recent work has studied the incidence and prevalence of cramping. (Schwellnus, Drew et al. 2011) Once again, these studies found that no difference in hydration or blood sodium concentrations between crampers and non-crampers.

However, two factors did emerge that separated crampers from non-crampers: the crampers ran faster (e.g., they were among the fastest, most competitive athletes) versus the rest of the field, and they had a history of cramping in previous efforts.

This is insightful: you cramp when you run hard, and when you have “the habit.” Since both exercise intensity and previous experience are central nervous systems, these findings support the neuromuscular control theory of cramping.

Salt Intake & Performance: The Pickle Juice Study

Athletes have known for a long time that salty foods and drinks decrease cramping and enhance performance. You start to cramp, so you stop at the aid station and dip that potato in salt. Or you pop the S!Cap. Then, within seconds, you feel better.

We just don’t know how or why. A recent study now sheds some light on that.

The intriguing “Pickle Juice Study” was performed in 2010 by a group of exercise scientists at North Dakota State University. The researchers exercised a group of subjects for a prolonged period of time to elicit the following effects: a water loss of 3% of body weight, a sodium loss of at least 145mmol in sweat, and onset of exercise-induced muscle cramping.

Immediately after all three conditions were met, the subjects consumed 75mL of pickle juice, while a control group drank 75mL of water (and a third group, no intake). The study found that, for both drinker groups, a reduction in cramping occurred in under 90 seconds, and the pickle juice reduced the duration of cramping 49 seconds faster, compared to a just-water group.

Because of this rapidity, the effect of the pickle juice could not have been due to changes in blood sodium or overall hydration levels, as insufficient time had elapsed for the stomach or intestines to absorb the salt or water. Moreover, a follow-up study noted that – even with sufficient absorption time – drinking 75mL of pickle juice had no effect on blood sodium (or hydration levels).

So, an effect was measured, but systemic changes were impossibly fast. What, then, caused the change?

The authors speculated that drinking the pickle juice – either through its salinity or acidity – triggered a neurological reflex, somewhere in the mouth or throat, that traveled to the brain. Therefore, it was a brain effect – not a GI or blood effect – that reduced the cramping. This study supports the neuromuscular muscle cramp theory, that the nervous system has ultimate control over cramping.

Noakes discusses this, as well, in the same podcast:

As far as sodium balance goes, we do not need to take sodium, because you will be excreting during the race any excess sodium you’d take the day before. And any excess sodium you take during the race will simply appear in your urine…. We know that, so you don’t actually need it to manage your sodium balance.

But there is a component we know, that the brain has a link to the tongue, and when you put salt on your tongue, the brain recognizes that you are putting salt into the body, and it may well modify your performance. We certainly know that if we put food in your mouth, particularly carbohydrates, but I think protein and fat, but they haven’t been studied yet… your brain immediately interprets that, ‘This is good!’, and allows you to run faster.

We know that if you’ve got a cramp, and you put a salty drink on your tongue, you will reduce the cramp, it will tend to break, within about 40 seconds. So that can’t be because of salt entering your intestine and being absorbed, it’s because the salt is acting through a reflex in the brain, and the brain is for some reason responding to the salt and saying, ‘OK, we mustn’t have muscle cramping at this time.’

Because muscle cramping is a brain/spinal cord phenomenon, and has got nothing to do with the salt balance in your body. So my point is… people may take salt, and they may say, ‘My gosh! It does improve my performance!’, and I would not discount that, but it’s not acting by improving the salt balance, it’s acting in the brain… it’s not confusing the brain, but it’s interpreting that salt is coming into the body and that is good, and therefore you can run faster.

Muscle Cramping & The Central Governor

Let’s review what we know (or think we know, or know what we don’t know) so far:

  • Muscle cramping is a neurological, “electrical” phenomenon, likely centered in the central nervous system, where reflexes become unbalanced, affecting the muscle.
  • The muscle is most susceptible to cramping with prolonged fatigue and (according to Noakes), when we “run faster than we should.”
  • Sodium or electrolyte balance – in the blood stream or muscle cell – has zero effect on cramping.
  • Sodium (and possibly water, sugar, and fat) tasting in the mouth (and possibly upper GI tract) does have a positive effect: dampening cramping and improving performance. But the rapidity of this effect suggests that it is the brain alone that creates this effect.
  • Muscles most affected by cramping are those repetitively used and confined to a small arc of motion.
  • The only known treatments to cramping are to slow down, stop, and stretch the muscle to a maximally lengthened state.

These concepts suggest that muscle cramping, therefore, might be an action of the Central Governor. Recall from last month’s column: the Central Governor protects the body from danger, and is likely the major determinant for running performance. As such, the mechanisms above suggest the brain is trying to protect the body – either the brain, heart, or muscles – from damage. And in this instance, that protective mechanism is cramping.

To add to that idea, Noakes notes that cramping might also be a protective response to chronic, micro-trauma to over-trained, over-stressed muscle tissue:

What we used to think of as muscle tears… now we’re beginning to think… it’s something to do with the fascia surrounding the muscle, that becomes irritated, and that then causes the electrical activity in the muscles to go up, and they start to cramp…. I think what we’re going to find is that injury is a part of it: if you’ve been training hard and the muscle fascia is slightly damaged in some way (that we don’t yet fully understand). Go out and race, and after a time, what happens is, the muscle starts to cramp a little bit, they’re too small for you to notice, and then all of a sudden, the whole muscle goes into cramp. But as it resolves, you find that there are these little nodules that continue to be cramping. And in my view, that is likely to be injury, rather than anything else…. It may be a protective reflex that stops you from running and damaging your muscle any more.

Put it all together: cramping, then, very well could be a self-preserving act: “This guy won’t slow down, he’s working too hard – I’m going to make him slow down.”

Based on these concepts, soothing the Central Governor is the key to treating and preventing cramps.

The List: Strategies to Treat & Prevent Muscle Cramping in Training & Racing

Based on what we know, I propose the following strategies to treat and prevent muscle cramping:

#1 – Run Sustainably

Through some mechanism – either neurological, cardiac, or neuromuscular – the brain judges your current effort and decides whether or not it is sustainable. Maintaining an unsustainable pace early in a long ultramarathon may trigger the onset of muscle cramping. Why this happens, in absence of energy deficit or other perceived physical duress, is unclear.

That said, if you have a cramping issue – make note of the paces and conditions (heat, altitude, terrain) at which cramping occurred. Adjust your pace downward, accordingly, and gauge the effect.

An even better way to gauge sustainability is to use a metric, such as heart rate. Heart rate is all-encompassing: it takes into account those variables, as well as fatigue, anxiety and stress, and tissue trauma. If heart rate is high, your system is stressed, and needs a break.

For me, I failed to make any adjustment to pace or effort at this year’s Western States 100: I continued onward with little slowing, or stopping. My cramps continued, unremittingly, and irreversibly, as a result.

Conversely, it’s worth noting two successful examples of cramp-management at last week’s Western States. Firstly, was iRunFar’s Andy Jones-Wilkins. As noted in his race report:

By the time I rolled into Robinson in 53rd place my quads and hamstrings were cramping pretty intensely, so I knew I had to top off pretty aggressively on electrolytes.

My plan from the outset was to spend a bit more time at the early aid stations to make sure I was taking care of myself and dosing my effort sufficiently to have legs from the River in. However, the eight minutes I spent at Robinson Flat were, perhaps, a bit too long…. I ate my yogurt/granola concoction, topped off my fluids, and had a double shot of “Witch’s Brew” (double strength chicken broth made with coconut water), so I ultimately didn’t get out of there until 10:45, a full 15 minutes slower than my planned split.

The question is, what decreased the cramping? Was it that barely-potable concoction of salty fluids, or scores of S!Caps? Or was it simply stopping at the aid station for nearly ten minutes – and resting the skeletal and cardiac muscle – that decreased the cramp response?

The research would suggest it was the rest, not the “Witch’s Brew,” that was successful.

Additionally, ultra veteran Scott Wolfe raced himself to an impressive 11th place male finish, noting that he took two prolonged breaks, lying in both the Middle Fork American River (mile 45) and Volcano Creek (mile 60) “until my heart rate got below a hundred” beats per minute. Was it the cooling effect that aided performance, or simply stopping and allowing his muscle tissue to rest? We don’t have a definitive answer, but again, the research suggests it was the resting of muscle tissue that was the primary benefit. However, cooling the system also provides vital positive input to a cautious, stressed-out Central Governor.

Either way, these decisions paid off in a big way for both Andy and Scott: they ran sustainably and kept the Central Governor appeased throughout the day.

#2 – Run Efficiently!

Given what Dr. Noakes stated about repetitive muscle use playing a role in cramping, it is vital that the run stride be as efficient as possible. Muscle groups such as the medial quad and calf tend to cramp because these groups bear the brunt of braking forces in an efficient stride: a foot strike too far in front of the center of mass causes excess force absorption, “braking,” to occur in these groups. An efficient foot strike will minimize stress on these groups.

Moreover, having a compact, but balance stride will also help: as Dr. Noakes notes, muscles that function in a “small arc” – or small pattern of movement – are most susceptible to cramping. Having adequate hip and knee flexion/extension provides maximal range of motion and “stretch break” for the working muscles.

Be form-focused!

#3 – Ply the Central Governor With Its Favorites

Low salt doesn’t cause cramps, but taking small portions of salt helps. Keep the Governor happy with frequent – but measured – doses of its favorite go-to food groups: water, salt, sugar, and even fat. Maintain a “see-food diet”: if it looks (and tastes) good, eat it. The Governor will be pleased, and allow for improved performance.

But don’t take this too far. The diminishing law of returns is a steep slope: over-doing water, food, and salt are dangerous, their effects ranging from general malaise (in the case of a sour or full stomach) to dire (hyponatremia).


Cramping is a neurological phenomenon. So is pain. If cramping, like pain and other complex neurological processes, are of central origin, we, then, have more control than we realize. In discussing the physiology of pain, we noted the impact of stress, anxiety and mood on pain – and how it acts as an amplifier of electrical (and chemical) signals.

If this is also true of cramping, we do have some conscious control.

Cramping is a threat to performance. Threats cause tension. Cramps are neurological tension gone overboard.

Defuse the threat. Recognize that anxiety, worry, and grief about cramping – and its impact on your performance – may increase its severity. Conversely, simply relaxing and – taking it to the extreme – going out of one’s way to smile and even laugh – may have a potently dampening effect!

Anecdotal evidence exists for this: me. In reflecting after Western States, I remembered this experience near the end of my 2011 North Face Endurance Challenge race:

I fought the blips constantly, as if tip-toeing across a mine field –one false move and it was a death of tetany, and at best a painful limp to the finish. At worst? A DNF.

Strategizing, I realized I needed total relaxation. Moreover, I had to smile. So I did. A huge, ridiculous grin, almost non-stop, was pinned on my face as I floated along down the road and onto the final climbs…. I had to soften it as to not look insane as I passed a Park Ranger in his squad, then a random aberration of [Dave Mackey] running downhill past me. “Hey Dave!”, I said, the smile slightly less ridiculous. But it worked!

Indeed, after spending hours that day, literally eating Nuun electrolyte tabs (deserving of a trip to the periodontist, post-race), what ultimately resulting in the cramps ceasing was relaxation: smiling, and – albeit forced – laughing out loud. The cramps abated and did not return for the remainder of the race, despite maintaining and ultimately increasing pace at the end.

#5 – Slow down.

Should those mid-run strategies fail to curb cramping, you must slow down. Period. Again, the science states that – outside neurological disruption – a slowing of pace – thus lowering the demand on the muscle and nervous system – is required.

Slow down. Gauge the effect. Should cramps alleviate, gradually increase pace, as tolerated.

#6 – Stop. Stretch. Ice.

Should slowing fail to stop the cramps, it is time to stop running. Walk, or stop at an aid station. Per Noakes: stretch the repetitively-shortened muscle with copious stretching. Also try icing, as much for the neurological input as for cooling. Ice is a frequent tool for health-care practitioners to use to “break” (or decrease) high muscle tone in neurological patients.

#7 – …Know When to Fold ‘Em.

Should cramps persist and muscle cramps segue into severe muscle pain, perhaps it is time to stop. This is a deeply personal decision, depending on your race goals, that point at which you are at in the race, and personal experience.

But recognize that, with severe muscle cramping, pain, and greatly reduced pace, the brain is trying to tell you something: you’ve over-done it, tissue is compromised, and you need to stop. Ultimately, it is up to you as to whether you listen to that message. If we always stopped when the brain said so, no one would ever finish an ultra. However, much severe suffering might be avoided by doing a better job of listening to the body, early and often.

* * * * *

Knowledge is power, and muscle cramping is the body telling you that something isn’t right. Listen to the body, recognize that there is a problem, and act accordingly. Few things are more rewarding than problem-solving, and over-coming obstacles, in training, racing, and life. My hope is these nuggets will help you solve your problems and “keep moving to the finish line.”

Call for Comments (from Bryon)

So, it’s probably unnecessary to make an express call for comments here, but

  • When have you experienced cramps in the past? Do the above stated causes likely apply?
  • How (do you think you) have you resolved cramps in the past?
  • What are your thoughts on the growing evidence for mental stimulus greatly affecting physical performance during endurance sports?
Joe Uhan

Joe Uhan is a physical therapist, coach, and ultrarunner in Auburn, California. He is a Minnesota native and has been a competitive runner for over 20 years. He has a Master’s Degree in Kinesiology, a Doctorate in Physical Therapy, and is a USATF Level II Certified Coach. Joe ran his first ultra at Autumn Leaves 50 Mile in October 2010, was 4th place at the 2015 USATF 100k Trail Championships (and 3rd in 2012), second at the 2014 Waldo 100k, and finished M9 at the 2012 Western States 100. Joe owns and operates Uhan Performance Physiotherapy in Eugene, Oregon, and offers online coaching and running analysis at