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In reading the labels on so many nutritional products lately, you can see that the sodium content in different products is all over the map. So it's clear that different manufacturers subscribe (or unsubscribe) to different versions of the salt-during-endurance-exercise theory. Same goes for potassium, calcium, magnesium, etc. There was that one study at Ironman South Africa from a few years ago that studied sodium levels in 400+ of those athletes, and the conclusion was that sodium supplements had no bearing on performance or cramping. Well, this is certainly an interesting new take on why cramping occurs - worth considering. Will be good to finally get to the bottom of it.



Interesting stuff! After several years of using the Performance Management Chart, I've noticed that I tend to cramp more often in races when I'm "fresh" and my TSB is high (>+15). I've never cramped in a race when my TSB was negative. A couple of thoughts: when very fresh with a high TSB, my legs usually feel great, and maybe I just push myself harder early in races and then pay for it later. Or perhaps a slight bit of fatigue helps suppress the neuromuscular mechanisms that cause cramps. Curious if anyone else has observed this?

greg Hinrichsen

My educated guess is that cramps are caused by fatique and that the brain steps in to prevent further exercise/contractions as per the Central Governor Theory proposed by Noakes in "The Lore of Running." All to protect the body from self destruction. When you break a bone the brain steps in and uses the surrounding muscles with swelling, pain, immobility, rigidity, to make a cast. Perhaps some athletes are more sensitive and their brain steps in sooner. In a very recent case a professional triathlete was having persistent abdominal cramps and pain during competitions. After a couple years of frustration, he was eventually dignosed through an MRI with a stenosis in his left common iliac artery, the major blood supply to his left leg. It could be argued that his brain was using the abdominal cramps to alert him to the problem with his blood supply, or just preventing him from doing further damage, even though the actual problem was in another area of his body. It's the brain saying "Don't do that anymore." In a way it's consistent with your nervous system theory.

Don Haywood

For me - cramping is (apparently) mostly due to bike frame configuration.

For example, I used to cramp up all the time when in a longer road race after about mile 60 when riding my first racing bike (a TREK).

I then switched to Italian bikes (Colnogo and BMZ) and cramping quit. I then switched to a Giant compact frame - no cramping. Next bike was a TREK Madone - cramping started again. I sold the Madone after a year, bought a new Giant and no more cramping.

I'm not trying to dis TREK - in fact, my TT's were faster on that Madone because of the more forward position forced by the frame geometry. But the frame geometry made it impossible for me to get the correct fit - and that translated into cramping up. No change in stem, cranks or seat would let that bike fit me right.

It's just from personal experience but I think that frame geometry should really be part of the equation.

Jennifer Sage

So does this mean we should toss our Nuun or other electrolyte drinks (without carbs)? Or does there exist other benefits to these drinks beside "anti-cramping"? I for one have never cramped when exercising, only when sitting in a movie theater or stretching too hard in bed - and only maybe only a handful of times in my life. But I religiously take in electrolytes when riding, especially when it's hot or I sweat a lot, because I've "been told" that it is good for me. Is it still?

I'd appreciate your thoughts.

Joe Friel

Jennifer--Amy S asked the same question. See my response to her.

Jeff Patterson

Back in my days of Texas High School 5A Football in the mid-80's, I had horrible calf and hamstring cramps in those late fall games where temps would DROP way way down into the.....50s. I know, freezing cold. I never cramped during summer two-a-days in the 100+ degree heat, but low temps destroyed my calves and hamstrings. Our trainer would have me hauled over to the sidelines and he would give me a squeeze bottle full of....pickle juice. Great blog post, Joe. Doesn't surprise me at all.

Shane Brown

I rarely cramp during a hard workout. However, I do cramp occasionally while sleeping or getting up from sleeping after very intense workouts. What is your take on stretching, could it help with cramps? I was told by a physical therapist that the best time to stretch is after a 20 minute warm-up, and don’t bother at the end of the workout.

I drink GA and Accelerade during workouts. I also eat peanut butter filled pretzels and various cereals while riding and take one E-cap per hour. After a workout I eat and drink a protein drink or chocolate milk.

I am going to give your water instead of sports drink a try. Seems like a good way to cut out unnecessary calories.


Joe Friel

Shane--Stretching the cramping muscle while it is cramping indeed does help stop the cramping. So some reserachers believe general muscle stretching may also help with prevention. But there is nothing definitive.


Thanks for this article Joe!

I too suffer from horrific cramping - some of my training partners have had the opportunity to witness it and were horrified as I go BIG when I do cramp... when my legs cramp ALL my major muscles in my lower body cramp to the point where I can't stand up straight or sit down as my body goes into a 'lock-down' from which it's pretty much impossible to recover either way.

With this year's Ironman SA race I felt more rested and better prepared than the previous year but for some reason started cramping early in the bike leg and couldn't recover. At one stage during the run I sat down on the curb - my hamstrings and calves went into a cramp and I couldn't manage to get my legs straight. I had to struggle to my feet while standing on my toes and limped to a street light and struggled for a while to force my heels down.

I can very well believe that cramping is related to dysfunctional nerves (to put it in layman's terms). Since Ironman and the terrible cramping I experienced this year I have a spot on my left quad where the skin feels 'dead' to touch and hyper sensitive at the same time... might be nerve-related and would be interesting to see whether it could be related to the cause of my severe cramping. I've had similar 'nerve-issues' during the past as well.

I will definitely be trying out the pickle juice! :)

Racer Ex

So it's bunk that hydration or sodium influences cramps. But you drink a sodium rich fluid and the cramps diminish in intensity. They couldn't measure the increase in hydration so despite the fact that you provided them fluids, they aren't rehydrated at all.

I love science. But there are times when we decide our nose is a collection of cellular DNA and not, in fact, a nose.

While we may not know the exact mechanism that causes cramps, we do know that cramps are fairly common in any number of circumstances where dehydration is present and that a common side effect of diuretics is cramping.

We also know that some people are more prone to cramping than others. So I'm leery of conclusions drawn from a small sample group who's cramps were artificially induced.

Personally, I fought with cramps for years. Over the last two seasons I developed a feeding and fluid/electrolyte replacement protocol that's kept me essentially cramp free. I'm sure my study on this wouldn't pass any scientific muster, but it seems to increase my winning percentage.

Racer Ex

And a bit of clarity on my previous comment, I'm not saying that cramps are ALWAYS caused solely or even partially by be hydration or electrolyte imbalance; it would appear that there's a multiplicity of causes and mitigations for cramps. I think the issue is less the exact biomechanical condition, but the circumstances that create the condition. Anecdotally that would appear to vary from person to person.


Hi Joe,

I think your theory about muscle cramping makes pretty good sense.

If you think about who has the worst cramping / muscle spasms, it's people with MS. It's all neurological and doesn't have anything to do with hydration.

I wish it's weren't the case, I'd love to be able to to toss down a few bottles of gatoraide and not have to worry about my legs seizing up in the middle of a lake :D.


Ricardo Bonegio

Thanks for this helpful article. I race Vets MTB in the UK, and have been struggling with cramp in the longer races, despite being careful about hydration and electrolytes. I feel great going at full tilt for about 2.5-3hrs, and then wham - its like hitting a brick wall - quads and hams just seize and it takes ages to stretch them out and get going again. I've been coming up with my own (rather obvious) strategy, of more long distance training and better pacing, but have been very frustrated by the lack of good advice on this particular topic.

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