In this episode of the Athletes Compass podcast, hosts Paul Warloski and Marjaana Rakai dive into the contentious issue of muscle cramps with sports science expert Dr. Paul Laursen. They explore two prevailing hypotheses: the common belief that cramps are due to electrolyte imbalances and dehydration, and the neuromuscular hypothesis which posits that cramps stem from unfamiliar tasks and neuromuscular fatigue. Through detailed explanations and personal anecdotes, the discussion reveals compelling evidence supporting the neuromuscular perspective, emphasizing the importance of context-specific training and preparation. Listeners are encouraged to rethink conventional wisdom and adopt more tailored training strategies to mitigate cramping.

Key Episode Takeaways

  • Muscle cramps are more likely caused by neuromuscular issues than electrolyte imbalances.
  • Lack of task familiarity and neuromuscular fatigue are primary contributors to cramps.
  • Proper preparation and context-specific training are crucial in preventing cramps.
  • Industry promotions of electrolyte solutions lack robust scientific support.
  • Acute cramp relief can be achieved through stretching to reset neuromuscular communication.
  • Post-exercise nutrition should include a balance of proteins and electrolytes.



Paul Warloski (00:27)

Hello and welcome to the Athletes Compass podcast where we navigate training, fitness and health for everyday athletes. We have all had them, at least most of us have had them at the most inopportune moments, muscle cramps. Cramps sometimes come out of nowhere. Sometimes we can feel them coming miles away. They are always painful. And as we've seen many times watching sports, even top athletes get them. It seems though,

that some people tend to get cramps more often than others. Commonly, we all think that cramps are caused by electrolyte imbalances, but Dr. Laursen you have another perspective. What's the deal with muscle cramps?

Paul Laursen (01:11)

yeah, this is a little bit of a controversial one, Paul, in the world of sports science and nutrition and all that. And of course, yeah, we have two prevailing hypotheses. One is, as you mentioned, the water and electrolyte hypothesis. And that is that cramps are being caused by a depletion of electrolytes or dehydration or some other nutritional issue. And then there is another group.

Paul Warloski (01:16)


Paul Laursen (01:41)

that you'll know which side I'm on. But it's where the hypothesis is that cramping is really a neuromuscular issue that tends to be due a little bit more to a lack of familiarity with the task that you're doing in the context that you're doing. And it's called the neuromuscular hypothesis.

So that's what we'll talk about today, Paul. What makes a little bit more sense, the electrolyte dehydration hypothesis or the neuromuscular imbalance hypothesis? So, yeah.

Marjaana Rakai (02:23)

going to jump right in here and maybe this will reveal which camp I am in. I've never had muscle cramp before, like before Ironman Texas, like not during race or, or a training session. On the swim, my calf cramps. And then on T1, my left side ab cramps and on T2, still on the bike coming into T2, the same side.

cramps again. On the swim, does it make sense that it's caused by electrolyte imbalance? I'm well hydrated. To me, it doesn't make any sense that I would have a cramp during the swim. But why I think it's a neuromuscular mechanism behind it, fatigue or unfamiliarity, to me,

Thinking back, what happened a couple of months before Ironman Texas, I hurt my back and I went through some chiropractic and some treatments and we found imbalances in my core and posterior side. So to me, that makes perfect sense that left side cramps, it was left calf and left ab, because there was some kind of imbalance.

in the system still. Was I dehydrated? I don't think so. So I'm in the same camp.

Paul Laursen (03:53)


We better explain a little bit more because it's pretty easy to, at first glance, to think about what the issue is for the electrolyte dehydration imbalance hypothesis. You're depleted in electrolytes, you didn't get those right, or you're dehydrated. Of course, you've just said, Marjaana, that you had your starting kicking off in the swim first phase of the triathlon where...

unlikely that that's to be the case, right? You're well hydrated. You're all ready for this race. But yeah, so what else? Let's move over to the neuromuscular hypothesis. And what are we talking about? And to understand it more, we need to go a little bit into the weeds of physiology and think about some of the neuromuscular nerve receptors and sensors that are in

Paul Warloski (04:46)


Paul Laursen (04:56)

our musculoskeletal neuromuscular system. And there's two main ones, there's a number, but the two big ones in this hypothesis is one called your muscle spindle. And these muscle spindle are little sensors that are in every muscle fiber that talk to the nerves, that go back to the spinal cord that...

and they talk about basically, what do they do? Like I think sort of tension ultimately, like stretch sensors that are actually within the muscle. So if your muscles kind of stretch, the muscles itself being stretched, they're telling your brain and spinal cord about that stretch. And then we've got another one also looking at tension and it's called the Golgi tendon organ. And it sits in all of your...

your tendons, right? Like in the tendons, remember, are what the bones attach to the muscles, right? So every time your, your Achilles tendon is one that we all know. Like that's our largest tendon in the body is the Achilles tendon, right? So, but of course you've got tendons, you've got muscles attached to so many across the whole musculoskeletal system. So it also is talking to the brain and spinal cord. Now what,

winds up happening in this hypothesis is that there is some, there's always this chatter that's going on that is kind of, we're not really familiar with it, but it's because it's unconscious, but there's this chatter between the muscle spindle and the Golgi tendon and the spinal cord to make sure that your coordination is correct. And that cord, that...

Paul Warloski (06:38)

Thank you.

Paul Laursen (06:44)

you know, that chatter is there for a reason. It's there to make sure that everything is going on in our body is right and makes sense. And we're, you know, we're not going to injure ourselves. But all of a sudden, when we're doing something that's unfamiliar and we haven't done before, there's sometimes this reflex that occurs and it causes the muscle to cramp and spasm.

Paul Warloski (07:00)

Thank you.


Paul Laursen (07:13)

And the thinking is, is that that spasm, that cramp is there for actual reason. And it's there to stop you from hurting yourself further. You're basically, it's just a little kick in the ass to remind you that, hey, we're not, this has not been done before. And you need to really, you know, think about continuing along this way, or you're going to harm me, the whole organism.

Paul Warloski (07:24)

Thank you.

Thank you.

Paul Laursen (07:41)

Right? So it's like, well, let's just work on a simple set, simple small area first and break that one down to make, you know, to bring you back to homeostasis or balance in your body. So that's the hypothesis that all of the data tends to more support. And a lot of studies have been done where they've actually looked at the electrolytes and dehydrate, you know, water components alongside the incidences of these cramps. And.

Martin Schwelness in South Africa has been a leader in this along with Tim Noakes. The data never supports it. But what does tend to support it is lack of preparation or going too hard relative to your threshold. In other words, because think about racing, you're so excited to get out there and do your thing. And we always tend to push a little bit more than...

Paul Warloski (08:25)

Thank you.

Paul Laursen (08:39)

then is maybe prepared for. And as a result, that's kind of, that's the kicker. So yeah, that cramping occurs. And back to you, Marjaana that's kind of where, you know, there was some issues along the preparation and maybe there was some certain areas in your body that weren't as prepared as possible. And don't forget the preparation needs to be context specific. So all of a sudden, if you throw heat into the,

into the recipe or into the concoction of stresses that you're getting, well, that's an added stress too. And the Golgi tendon and muscle spindle, they need to be prepared for that as well. So yeah, anything unfamiliar, boom, neuromuscular response.

Paul Warloski (09:14)

Thank you.

Thank you.

Marjaana Rakai (09:26)

So bringing heat into pictures as an extra stressor, not necessarily that you get dehydrated or imbalances in the electrodes.

Paul Laursen (09:41)

That's right, yeah, no, the heat more in the, at least, you know, my way of thinking, you know, it's just an added stressor that's in that, you know, that chatter that's happening between the spindle, Golgi tendon, and the, you know, the spinal region where it's all being interpreted.

Paul Warloski (10:05)

This could be the hot take of the year here, but does water or do water and electrolytes play a role in muscle cramps at all?

Paul Laursen (10:17)

Well, the data doesn't support that it does. And if anyone's out there and they know of a study that, like an actual study that supports those, that hypothesis, please, you know, include it in the comments. And we'd love to hear about that study. But as far as I'm aware, there is no study. There is high level of industry push.

Paul Warloski (10:20)


Paul Laursen (10:46)

So there's a lot of industry companies that are promoting their products that strongly push that. And that's a very loud noise that's out there. But again, as a sports science professor, if I go through all the studies in the literature, I can't find any that support that hypothesis.

I can find a number that supports the neuromuscular hypothesis.

Marjaana Rakai (11:21)

So for example, people who experienced a lot of salt loss, like they can see the rings on their exercise clothing. If you look at any forum post, you can see athletes who sweat a lot and say, hey, I need more electrolytes so that otherwise I'm going to cramp and I need to drink two liters every hour and have really high solution.

electrolytes drink? Are they doing more harm than good with that thinking?

Paul Laursen (12:01)

Well, in fact, they might be actually. Yeah. Yeah. There's a, let's, let's back the truck up a little bit. And, you know, this is why what we're saying here is probably hard for a lot to believe because it's, it's hard for you to see any of the things that I'm talking about, right. In terms of a muscle spindle or a Golgi tendon organ and all these sorts of things. But it's easy to see the salt rings that are on our clothing.

But now we have to go into physiology a little bit more and the legend in the world that's really one of my colleagues, Tim Noakes, he wrote a book called Waterlogged and it's really talks a lot about the water, hydration, electrolyte imbalances. Fantastic textbook, highly recommend. And yeah, ultimately we have to think about the, what's the purpose of a, you know, an endocrine, the, sorry, what's the purpose of a sweat gland?

And there's a couple purposes. We've talked about it before on the Athlete Compass podcast. We've talked about the purpose of the sweat gland is to put water on our skin so that the water can be evaporated. Remember, we learned that it's the evaporation of the sweat, not the sweat itself that's going to be cooling. And that's why in a humid environment, it's really hard to cool yourself.

compared to a dry heat. Dry heat's way easier to stay cooler and that's because of the process of evaporation. Okay, so now we've dealt with that, but now we're talking about the salt that comes out of that sweat gland. And this is one of the other, so the other purposes of the sweat gland, it's called an eccrine sweat gland. And the job of the eccrine sweat gland is to get rid of the salt,

to make basically to make your salt level in balance in your body. Okay, so it's pushing out the salt level to get rid of the salt because the concentration of salt is too, is perceived by the body as being too high. So if you are seeing a bunch of rings of salt, you're, and it's like, it's crazy cake. You probably have actually,

more salt in your body than you actually need. They're doing their job of actually getting rid of that salt because they don't want to create a high concentration of that salt in you, right? They don't want to imagine like, you don't want a super high concentrate of salt in the solution necessarily. So they're regulating the balance. The other part in your body that does that is the kidneys. So the...

the bloodstream has two components in it that will regulate the salt, the kidneys and the sweat glands. So yeah, and basically if you are short of salt, what winds up happening is that you conserve fat. So they've done studies in, usually in soldiers where they basically don't give them any salt at all in their diet. And what those studies show,

And they're forced to do these things. They're not pleasant, but you get no salt in your diet in these studies. And what winds up happening is there is this retention of salt. The sweat glands just completely, like they don't get rid of it because they hold onto it and your kidneys do the same sort of thing. So yeah, basically we just have this system in our body that will always kind of regulate the amount of salt that we need. And you can count on that system in yourself.

Paul Warloski (15:27)

Thank you.

Paul Laursen (15:51)

to give you just the right amount.

Yeah, actually, I mean, just this literally came out days ago, but it's in the international journal, Sports Physiology and Performance. It's called the Effective Personalized Sodium Replacement on Fluid and Sodium Balance and Thermophysiological Strain During and After an Ultranterence Running in the Heat. So what they did in this study, they had nine athletes, seven male, two female. They did a five hour treadmill run.

Paul Warloski (16:18)

Thank you.

Paul Laursen (16:25)

in 30 degrees and they gave them in a double blind randomized crossover design. So they didn't know what they were getting, whether they were getting like sodium and they got it. So because there's these businesses there that are like, they're going to give you sodium to your sweat losses, right? Like they calculate out how much sodium you lose. So, you know, sports scientists go in there and say, okay, well, let's see if this actually has any basis. So.

You either got sodium capsules to the amount you lose versus placebo versus none. And what wound up happening after that five hour run is basically, what do you think based on, if you understood what I just said in the last five minutes of, what do you think should happen for those that are randomly getting the sodium pills versus the placebo? Marjaana

Were you paying attention? What should happen? Well, nothing happens for performance. Absolutely. I don't think they actually looked at performance per se because they're just running at a steady pace in that one. So what?

Marjaana Rakai (17:20)

Nothing, nothing, nothing happens. Not for performance.

So the people who got sodium just sweated out.

Paul Laursen (17:43)

There you go, good job. That's exactly what they showed. So those that took, and this, so no one knows what they're getting, right? But that's exactly what they found. So those that got the sodium tablets, they had higher urinary secretions of sodium and basically higher, I believe higher sweat sodium excretion as well. Yeah, so I'll just read the conclusion.

Paul Warloski (17:44)


Marjaana Rakai (17:47)


Paul Laursen (18:09)

personalized sweat sodium replacement during ultra -strengths running in the heat with ad libitum fluid exacerbated the rise in plasma sodium concentration compared to none. So they got, it did what it was supposed to do. It definitely raised the plasma sodium. You got into the bloodstream, but it did not substantially influence overall body water balance or physiological, thermophysiological strain. A large sodium deficit occurred.

During exercise, large sodium deficit incurred during exercise leads to substantial renal sodium conservation post exercise.

Marjaana Rakai (18:50)

and they were thirstier after? They drank more water after? Was that right? Like you would think like when you take lots of salt, like you get so thirsty afterwards, right?

Paul Laursen (18:58)


Yes, you do. Yes, you do. Yep. So yeah, actually, yeah, exactly.

Marjaana Rakai (19:10)

I'm just thinking, I'm just mentioning that because sometimes like when we do take those, like I used to be on that camp, like, okay, lots of sodium. I won't mention the name of the brand, but very high concentrated sodium, potassium. And then I would be so freaking thirsty all the time. Right? So when you take a highly concentrated electrolytes, you also get...

so thirsty. So you think that you need to be drinking a lot more water and you sweat high. It's you're actually your body's doing what it's supposed to be doing, getting rid of that salt, right?

Paul Laursen (19:53)

That's right. Yeah, that's right. And then you need to put it back after. Yeah, that's why it's giving you those signals, right? And that's why, and I believe you should always do that as well too. So this is where, you know, my belief, like a lot of meat products, you'll have a lot of salt that's in meat just naturally, even without salting it, but you could salt it too.

Marjaana Rakai (19:55)

And then.

Paul Laursen (20:18)

But this is why post exercise, a lot of protein sources with that, you know, you get salts at the same time, various electrolytes back. This is a good thing to have in the post recovery period. And, you know, we always talk about the importance of protein and stuff, but I think it's also the importance of the protein alongside the electrolytes that you're getting back after. Because yeah, we do get rid of those during exercise.

Paul Warloski (20:37)

Thank you.

Paul Laursen (20:48)

But yeah, back to cramping though. We're not really talking about cramping. There's no talk about cramping in this one, but again, there is no evidence for the cramping with more sodium replacement. Yeah.

Paul Warloski (21:05)

So I'm reflecting on what you said about the neuromuscular response to something that's unfamiliar. And I was out in Pennsylvania a couple of years ago doing a gravel stage race. And I had trained a lot because I had not done, you know, four days of, you know, 60 mile gravel races before. So I trained a lot, did a lot of four day, you know, training blocks, tried to get as,

was unfamiliar was the mountains. And in Wisconsin, we do not have mountains and I did not have, you know, 20 minute climbs where it was, you know, steep and rough. And I cramped so much on the first day, because I was also going hard in a race that it, you know, affected me for the rest of the race, because my muscles were just, you know, a mess. So what I'm understanding from you, I'm not going to lie, I'm not going to lie.

is that both the unfamiliarity of the mountains and going too hard likely cause those cramps.

Paul Laursen (22:14)

Absolutely. Yep. You got it, Paul. That says, yeah, I mean, time and time again, it's so easy to go back to the, you know, the hydration electrolyte hypothesis. But, you know, if you really look at your, the principle specificity alongside your training and alongside the activity that caused the cramp, there's usually a dissociation between the two. And.

Sorry, I'd always go back to Athletica, but this is what we do our best to try to help people with is to try to make those, especially in the build phase, the build preparation phase, we try to have components that you're probably going to experience in those types of races. So this is why short intervals are in there because you're going to have to have those punchy parts. This is why strength endurance, you know, intervals, you know, in cycling are in there because you're going to have to grind up these hills with high torque.

So yeah, if there's different ways that you can get that, especially if you're in a flat land and you're gonna have to go into a hilly terrain, let's try to prepare you as best we can from that. Then the heat one is a hard one and that's up to you to try to find some heat and again, go back to the heat preparation lecture that we've spoken around. Because yeah, that's gonna be another potential co -founder in there.

If, and if that isn't, you know, we, we always talk about these heat cramps, but that's usually heat acclimation. The process of that is usually the, the thing that's going to help you much, much more than anything you, you know, you carry on your person, by way of electrolytes or, or nutrition sort of products. You want to get the internal workings of the body, accustomed to that, what you have to perform in, first and first and foremost.

Marjaana Rakai (24:10)

Yeah, and if you look at Ironman races or marathons, those are already really hard to train for. But typically the cramps happen at the run part, right? Later into the run, 28 Ks, whatever, people start cramping. And it's really hard to train, swim, bike, and then run.

Like you can't do Ironman before you do an Ironman, right? So oftentimes that's when all the wheels start falling off, cramping happen at the later part of the races. So is there anything preventative that people can do other than train hard and train in the heat and train on the mountains?

Paul Laursen (24:55)


Marjaana Rakai (25:08)

prevent those cramps. Does strength training play a role?

Paul Laursen (25:13)

Yeah, that's a good point. So first of all, again, back to how you prepare is really going to be important. And remember, again, the Athletica model is where we're having pieces of that throughout the whole thing, because we can only really give you pieces of the race prior to the actual race itself. Because as you said, Marjaana, you can't, you just can't go and give the whole race, right? Like,

That's how I think when we were starting, we would sort of do that, right? We would do the best that we could to just do huge volumes of just doing these close to Ironman races repeatedly in training. But there's a better road to Rome and that's kind of more repetitive and principle of consistency is so critical too, right? But to your question on strength training, I think,

I don't know the answer. I don't know of any studies that have looked at that. However, anecdotally, I looked to my colleague, Martin Besheit, who in his NO1 experiments where he was doing these ultra long runs and the first time he did this ultra run, I think this was over like a two day period kind of ultra run. So it's like a hundred mile or kind of thing. And he just absolutely suffered big time.

and cramping and all that sort of stuff. And then the second time he prepared for it, he did, he added eccentric and much of the, you know, the strength training stuff that we know helps for the legs to prepare for a lot of that downhill kind of work. We know our legs are gonna get beat up in things like Ironman and ultra runs and the like, and having that, those eccentric contractions.

inside, you know, in the program. It makes sense that that would assist with the neuromuscular hypothesis, right? Because you're tuning the tendon organ, right? You're giving it that stretch that it needs. And yeah, that's because yeah, there would be, you know, there's going to be this natural breakdown as you, as when you hit like 28K in the marathon, like you just mentioned, Marjaana. So I don't have a study that shows that, but sometimes we have to just go with our gut.

make our best guess and that would certainly be a good guess to make for me.

Marjaana Rakai (27:48)

When do we, when we have those cramps during race, what should we do?

Paul Laursen (27:54)

Mm -hmm. Yeah, that's a great one. So, well, again, we can go back to what we've spoken about with physiology and we can talk about the Golgi tendon organ that sits in the tendon. And this is why, again, this hypothesis holds versus the electrolyte one is because we all know if we stop during a race and we're cramping and we can find a way to stretch that muscle group that...

then we find that the cramp is almost immediately alleviated. And that's because you're resetting the whole conversation, as we mentioned, between the spindle and the Golgi tendon organ. So by stretching that muscle out, you're stretching your, say it was your calf, and you're doing a calf stretch, or a hamstring, and you're doing a hamstring stretch, it almost, very quickly is alleviated.

Paul Warloski (28:28)

Thank you.

Paul Laursen (28:51)

Then of course you get going again and then it goes. But at least initially and acutely, you can completely alleviate it. And that's because... So that's really all you can do in an acute setting, Marjaana, is just stop and try to stretch it before you get going again. And then, of course, you probably need to lower your intensity of movement because that's going to be another important one. But...

Paul Warloski (29:12)


Paul Laursen (29:18)

to prevent it from happening in the first place. The hard news is that you just have to train harder and or longer or more intelligently. So that's all you can really do. And the more prepared you are, like, well, we often said there really shouldn't be too many...

surprises on race day when the preparation is done to perfection because you've done so many good portions of that race. You can go through your week and you've hit so many targets and pinch points in your race throughout the whole thing. Once you've done that, then the race is just an execution of what we know is under the hood.

Paul Warloski (29:49)

Thank you.

Paul Laursen (30:11)

less likely that any cramping will occur if the preparation is gone accordingly.

Paul Warloski (30:21)

But it comes from Levi, who's one of our friends on the Wednesday morning rides, but he asked about cramping during long high intensity efforts, you know, doing three hours at threshold or below threshold. You know, is there a pre -ride nutrition that could be done to prevent cramping? But I think our answer is no.

Paul Laursen (30:51)

Not that I'm aware of. And if anyone knows a one, I would love to hear it. I could use one myself.

Paul Warloski (30:57)

I did see something about magnesium that was singled out as an electrolyte, as an element that might be useful, but there was no... Because the study from South Africa was talking about sodium. Is magnesium something that we know anything about?

Paul Laursen (31:18)

Yeah, it's a good one, Paul. And there, you know, I have heard some, some discussions on that magnesium. You'll find magnesium in, again, in meat. So if you're having a meat predominant carnivore kind of predominant diet, you probably don't need to worry about it. But if you are more towards the vegetarian side, that could be something that is.

is helpful. Again, I haven't seen any studies that have looked at magnesium supplementation and cramping incidents. Again, if anyone knows of any that are out there, I'd be keen to hear what they discovered. But yeah, that's probably work that still needs to be done.

Paul Warloski (31:50)

Mm -hmm.

The takeaways this week are full of hot takes. We have got a bunch of good stuff. So cramps are likely neuromuscular issues that there is a, it is not an electrolyte or a water issue. It is a neuromuscular response to something that's unfamiliar. Number two,

If you have cramps, it is likely a lack of preparation or going too hard relative to threshold. So, you know, for your context that you're just not used to what's coming up, in the race. And if they happen, you need to back off. And number three, your preparation, you need to train harder. Do you need to be ready for the context specific training, whether it's heat, whether it's cold.

Whatever it might be, your training needs to be specific for that so that you are training more intelligently and more specifically for your context. Because in the words of Dr. Laursen, if you come up against something that's unfamiliar, boom, there is a neuromuscular response. And that's not always good because that can result in cramping.

All right. That is all for this week. Thank you for listening and join us next week for the Athletes Compass podcast. You can help us by asking your training questions like Levi did about, cramping in the comments, liking and sharing the podcast, giving us five star reviews and engaging with us on our social media for Marjaana Rakai and Dr. Paul Laursen. I am Paul Warloski and this has been the Athletes Compass podcast.

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