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Saturday, November 24, 2007

Muscle Cramps: Part III

A Novel theory for Exercise-associated muscle cramps

Today sees the third part of our series on muscle cramps. It was going to be the final installment in this particular series, but we've received some excellent and thoughtful questions and comments on the issue, so have decided that we'll do a fourth post, just summarizing some of those key "sticking" points. It seems from the feedback that this issue - electrolytes and cramps - is one of the more contentious ones around. So in our FOURTH post of the series, we'll look back and try to tie up any loose ends and conceptual issues.

In Part I and Part II, we have introduced some of the problems in the Electrolyte theory. These problems - gaps in the theory - are what Stephen Hawking referred to as "creaking, ugly edifices". In science, we establish a hypothesis, and when the data do not support that hypothesis, it is time to find an alternative. Clearly, the data on electrolytes do not support the electrolyte or dehydration theories (though they don't rule it out 100% either), so it's time for a new proposed theory. And that's what this post is all about...

The Muscle Fatigue and Spinal Reflex theory for Muscle Cramps

This theory has its orgins in a paper published in 1997 in the Journal of Sports Sciences, in which Professor Martin Schwellnus and some colleagues looked at the electrolyte-dehydration issue and concluded that on the basis of insufficient evidence, a new theory was required. They proposed, in this paper, that a cramp was the result of dysfunctional reflex control of the motor nerve as a result of fatigue. That sounds like a mouthful, and if we go into huge detail, then it could well be a very technical post. But we'll pull it apart step by step, hopefully without allowing the issue to become incredibly complex!

This of course means potentially oversimplifying things and leaving out some details that are not directly relevant, but hopefully it'll be understandable for everyone, and stimulating to encourage further discussions, where desired!

A summary of the theory

But because we know it's a highly technical issue, we decided to give you the "executive summary" right at the start. For those who like the detail, read on. For those who just want the answer, here's the take-home message:

  • Muscle contraction is initiated by a nerve, called the alpha motor neurone. The alpha motor neurone receives inputs from the higher brain areas (when you make conscious movements) as well as from the spinal reflexes
  • These reflexes are responsible for protecting the muscle against either excessive stretching or loading - they are the muscle spindles and Golgi tendon organs, respectively
  • There is evidence that fatigue causes increased firing from the muscle spindles, and decreased activity from the Golgi tendon organs
  • The net result of this change in the activity of these reflexes is that the alpha motor neuron activity is increased, and the muscle thus contracts involuntarily
For the detail, read on...

We begin with a brief overview of how muscle contraction happens in the first place.

Normal control of the alpha motor neuron

Your muscles are stimulated to contract by a group of nerves known as alpha motor neurons - in order for you to perform any motor task (touching your finger to your nose, cycling, running etc.), a signal from the motor cortex of the brain travels down the spinal cord, before leaving the spinal cord and traveling to the muscle fiber along the motor nerve. Once at the muscle, the electrical signal being delivered is responsible for muscle contraction (via a process we won't go into here).

There are other pathways that also affect movement, and of course, it's not so simple as a single impulse traveling down the spinal cord to the muscle - the complexity of a simple motor task, like placing your finger on your nose is absolutely astonishing, and it involves many other brain areas and muscle groups. But for our purposes, what is important is that when the alpha motor neuron activity is increased, then the muscle contracts.

The Reflex modulation of alpha motor neuron activity

Now, we can introduce a slightly greater level of complexity. We've just said that the alpha motor neuron is responsible for stimulating muscle contraction. This alpha motor neuron is itself stimulated by three pathways - any of these three pathways will activate the motor neuron and thus cause muscle contraction:

  • Firstly, there are the higher central control we already described above;
  • Second, you have spinal inter-neurones which we won't discuss in detail here;
  • Third, and most important for our cramp discussion, it's also regulated by what is called spinal reflex activity, and there are two particular reflexes that need to be addressed
The muscle spindle reflex

You've all probably heard of, or experienced, the classic "knee jerk" reflex, where a doctor (or a friend) taps on the knee tendon with a small hammer and you can't help but to kick out with your foot. Well, that simple test demonstrates the first important reflex.

The muscle spindle is a tiny structure in each muscle fiber, whose job it is to make sure that the muscle does not stretch too much. So what happens is that every time your muscle is stretched, the muscle spindle activity increases. This sends a signal back to the spinal cord (along what are called Type Ia AFFERENTS), where the nerve impulse is passed on to the alpha motor neuron, and then back to the muscle. Hopefully, you will see that the end result of all this is that the alpha motor neuron will be active, leading to muscle contraction - in other words, if you stretch the muscle, the response is to eventually cause it to contract - this is protective, and prevents over stretching of the muscle.

So referring back to the knee-jerk reflex, the tapping on the knee causes your quadriceps muscle to stretch. As a result, the spindle fires, the Type Ia afferent activity to the spinal cord increases, and then the alpha motor neuron activity increases. When the alpha motor neuron fires, it causes the SAME muscle to contract, and that is why your quadriceps contract and you kick out your leg in response!

The bottom line, if you would like to forget about the details above, is that if the muscle spindle firing rates go up, then the muscle will contract.

The Golgi Tendon organ reflex

Now, there is a second organ in the muscle that plays a role in reflex regulation - it's called the Golgi tendon organ. The Golgi tendon organ performs almost the opposite role to muscle spindle it monitors the tension in the muscles and tendons, and it is active when the muscle is contracted and lengthened (which puts load on the tendons). It's role is to make sure that the muscle does not contract too forcefully or under too much load. So when the muscle is placed under load (any contraction), the Golgi tendon organ fires, and it sends a signal to the spinal cord along what is called a Type Ib afferent (remember the spindles had Type Ia afferents).

This time, however, a key difference is that the Type Ib afferents tell the Alpha Motor neurones to STOP FIRING - they are inhibitory. In otherwords, when the Golgi tendon organ fires, then the alpha motor neuron activity goes DOWN. This would cause a reduction in muscle contraction. The effect, of course, is again protective, because it prevents the muscle from taking on too much load.

So, the bottom line here is that if the Golgi tendon organ is stimualted, the end result is that muscle contraction is switched off. However, if the Golgi tendon organ is inhibited, then the alpha motor neuron activity will increase, and the muscle will contract even more - this is called "disinhibition".

So what happens with fatigue, and can it explain cramp?

In studies of muscle function and fatigue, the following has been found:

  • When muscle becomes fatigued, the firing rate of the Type Ia Afferent fibers from the muscle spindle INCREASES;
  • and the firing rate from the Type Ib Afferent fibers from the Golgi tendon organ DECREASES.
Remember, we previously explained that Type Ia Spindle activity will cause the muscle to contract, whereas Type Ib Golgi tendon organ activity will cause the muscle to relax. If the Golgi tendon organ is then inhibited, the muscle will contract.

Therefore, FATIGUE causes the following:

  • Spindle activity increases - alpha motor activity increases - MUSCLE CONTRACTION
  • Golgi tendon organ activity decreases - alpha motor activity increases - MUSCLE CONTRACTION
So you can see how fatigue could very easily explain a sustained, involuntary muscle contraction, because it switches on alpha motor neuron activity.

This theory is supported by a number of observations, which cannot be explained by the serum electrolyte depletion theory:

1. Which muscles are more likely to cramp?

This is a pretty important question. The answer, of course, is the active muscles. This theory explains why, because the fatigue, which alters the activity of these two important reflexes, is most manifest in the active muscle. The electrolyte theory doesn't explain why only the muscles being used for exercise tend to cramp - in fact, if low electrolyte levels were the cause of cramp, we'd expect generalized cramping, as occurs in clinical conditions where people lose a lot of salt and become hyponatremic. It does not happen in exercise, but the Fatigue Theory can explain it.

2. What kind of muscle cramps most often?

Here, the answer is that a muscle that crosses two joints will cramp more often. This makes sense according to the Neural Fatigue theory, because if a muscle spans two joints, then it means that the muscle is going to be in a shortened position when it contracts. Think of the calf muscle during swimming - your toes are pointed (the ankle is in plantar flexion), which means the muscle is contracting in a shortened position. When the muscle is in this position, then the activity of that Golgi tendon organ is going to reduced even more than normal. Add to this the contraction, which stimulates the muscle spindle, and the net result is that the inhibition of the motor neuron is reduced even further, predisposing one to cramp.

This is why calf muscle cramps are so prevalent in swimmers (the only time I've ever cramped, incidentally), and also why, when you wake up in the middle of the night or sit in a strange position for a really long time, it's when you point your toes that you suddenly go into a fully-fledged cramp!

In other words, it's actually the position of the muscle that predisposes to cramp.

3. When is cramp most likely to occur?

Here, the answer is a little less overwhelmingly in favour of the neural fatigue model, but it is still a good argument for it, and against the electrolyte theory. The answer, of course, is that cramps happen during racing and not training, and it happens only at the end of the race, when the athlete is most fatigued. One could of course argue that it's only at the end that the electrolyte levels drop to the point where it causes cramps, but we described in Part II that there's zero evidence for this. So the explanation now would be that the muscle becomes more and more predisposed to cramp as it fatigues.

Supporting this, Schwellnus et al found that Ironman triathletes who paced themselves poorly and tried to cycle or run faster than they were capable of (based on previous performances) were going to be the ones to cramp. In other words, if a guy was capable of a 6 hour 180km cycling leg in the IronMan, and he tried to do it in 5h45, he would cramp. Note that this has nothing to do with electrolytes - he replaces the same amount, would lose the same volume of fluid, but he cramps because his muscles are not able to do the work he is asking them to! The resulting fatigue is what causes the cramp.

4. Is there any evidence for the theory?

The entire theory is built around this "end-result" that the activity of the alpha motor neuron is increased, due to the increased firing from the spindle Type Ia and the Golgi tendon organ Type Ib afferent fibres. Well, there is evidence that this is the case - the electrical activity of the muscles of cramping runners was measured after the 56 km Two Oceans marathon, and it was found that the alpha motor neuron activity was HIGHER than in non-cramping athletes.

Note that the electrolyte theory cannot explain this finding. Even more important, with 20 seconds of passive stretching, the EMG activity goes down. This means that stretching relieves cramps. Why would this be the case if electrolytes were to blame? Surely if the cause was low electrolyte levels, then the only solution would be to replace them? But instead, the most effective treatment is stretching, and it has been shown that the alpha motor neuron activity goes down. The act of stretching restores the normal balance, because suddenly, the Golgi tendon organ activity goes up again, and the muscle eventually relaxes.

Of course, this evidence is by no means the "definitive proof," and as Jonathan mentioned in Part II, we need to figure out a way to study cramps in a controlled, prospective fashion. Then we would be able to analyse exactly what is happening. Until that happens, we have theories and models. But this neural fatigue theory is certainly the best available theory for the observations of cramps at the moment. I have little doubt it will evolve over time, however!


Well done if you made it this far! I realise this is a pretty heavy post, and it relies on some level of physiology or anatomy knowledge, because there's a lot of jargon in the theory. That's something we prefer to steer clear of, but for this particular post, I felt it important to put out the necessary details. Of course, for some, we have probably oversimplified it, and please feel free to ask question.

For the others, the take home message really is that "Fatigue causes cramps, by interfering with the normal balance of spinal reflex control - it switches on the alpha motor neuron and the muscle contracts involuntarily."

Monday's post, which will be Part IV of the series, is a recap of some of the key issues in the electrolyte-fluid-cramp debate. I promise it'll be less technical than this one!



Anonymous said...

Hi Ross & Jonathan

Thank you for another interesting article.

You mention that the muscle spindle reflex is activated when a muscle is stretched and overactivity in the associated Type Ia afferents is in part responsible for cramping.

Wouldn't stretching a cramping muscle trigger the muscle spindle reflex, increase the activity in the Type Ia afferents, and make the cramp worse?

Or does the stretch increase the load on the muscle, triggering the Golgi Tendon organ reflex, and thus restore balance?

Ross Tucker and Jonathan Dugas said...

HI Mark

Good one! You're quick on the uptake!

As I was writing this post, I was in two minds as to whether I should actually go into detail on the reasons behind this, and I eventually decided not to...but based on your question, i think I will edit the original post and explain this a little more clearly - I was concerned we were getting a little too technical.

The answer to your question does get a bit technical, but I'll go for it anyway, and feel free to ask again if it's unclear.

The answer is a bit of both, but particularly the Golgi tendon response. When the muscle is stretched passively, the stretch is taken up by the muscle-tendon junction, where the Golgi tendon organs are situated.

So the way the muscle is designed, they're in the perfect spot to detect the stretch/tension in the muscle. Under normal muscle conditions and activity, if you lift a very very heavy weight, the muscle contraction causes the same type of stretch on muscle-tendon junction, resulting in immediate relaxation of the muscle. Think of a weightlifter lifting a weight that is just too heavy - he gets it off the ground, and then the muscle gives way, because the muscle was in real danger of damage because of the huge tension being applied to that muscle-tendon junction.

So passive stretch ultimately inhibits the alpha motor neurone activity for this reason - it activates the Golgi tendon afferents. Remember that cramp is most likely to occur when the muscle contracts in its shortened position, when there is very little tension on the muscle-tendon junction. So any stretch will at least partially undo this situation.

And what is key here is that when the stretch is being held, the tension in the muscle and tendon remains there - this means that over time, the firing of the inhibitory Type Ib afferents is also maintained. You'll see why this is important when we consider the muscle spindle a little lower down.

Now, to add to the complexity, and which you've been sharp enough to pick up on, the initial stretch of the muscle does increase the firing rate of the muscle spindle afferents, which in theory would cancel out the other effects. In reality, this does happen immediately when the muscle is first stretched - if you have a cramp, the last thing you actually want someone to do is to stretch the muscle, because for the first few seconds, it's even worse than before!

I recall that while in the medical tent at the Comrades Ultramarathon (90km) last year, one of the top 5 finishers in the women's field came in with major cramping in the calves. She was kind of stable, provided the ankle was in more or less a neutral position. Unfortunately for her, one of the physios treating her decided to start the rub-down process and put her immediately into plantar flexion - pointing her toes downward.

As you'll know from this post, what that does is unload those Golgi tendon organs even more and she went into even worse cramp. It got worse, because the next physio realised that stretching was the answer, and so began the stretch process. Of course, this only makes it worse FOR A FEW SECONDS, so she was not a happy patient for for a moment there, but within a few seconds the pain does subside.

What happens with the spindles is that the first response to passive stretching is that they increase their firing rate - as you correctly point out. However, the structure of the muscle spindle allows them to soon settle on their new length, and then the firing rate slows a little. The actual details are complex, but basically, a spindle itself consists of muscle fibres (called intrafusal fibres) running in among the normal muscle fibers (called extrafusal). The Type Ia afferents are wound around the intrafusal fibers (there are also different types of them, but we won't worry about that now).

When the muscle length first changes, it is the stretching of the intrafusal fibers that causes the Type Ia afferent activity to increase, and the muscle contracts. However, the system is dynamic, in that a new stable length is soon reached, partly passively and partly through the activity of other neurones. But the net result is that the firing rate soon decreases.

This, incidentally, is one reason why, when you are doing stretching exercises, you will find that you reach a "limit", but that if you hold it there for a few seconds, you can later push past it. That's why you might struggle to touch your toes right away, but after maybe 30 seconds of gradually working your way through the stretch, you might get there.

Anyway, the theory then is that the stretching of the muscle changes the firing rate of the alpha motor neuron by stimulating the Golgi tendon organs, and slowing down the rate of discharge of the spindles, though intially, that doesn't happen.

Hope that clears it up a little - it's a very confusing area, I must say, even for us to figure out and explain.

I'll make some slight changes to the original post later


Anonymous said...

That's a very interesting article! Would it be best to take the additional electrolytes through simple juices or by supplement?

Meg & Dave said...
This comment has been removed by the author.
Ross Tucker and Jonathan Dugas said...

Hi Anonymous, and thanks for the question about electrolytes.

In fact it is not necessary to ingest any electrolytes during exercise. These things do enhance the absorption of fluid from the guy and into the blood, but they are not an essential requirement during exercise.

Therefore one does not need to ingest one drink for the fluid and energy, and another just to get the electrolytes.

If you tolerate well and enjoy the juices to which you have referred, then I would suggest you stick that that product providing it supplies sufficient carbohydrate (about 30-60 g per hour).

So again, it is not necessary to take a supplement only for the electrolytes.

Thanks again for participating in this discussion!

Kind Regards,

Anonymous said...

Great work gentlemen. This is very interesting stuff. I appreciate all the detail, which I have not yet fully digested. I posted a few days ago because I have suffered from infuriating calf cramps in several marathons. I've run 13 and cramped in 4 or 5. A few times, I've been right on the border, where my calves tingled and told me that if I went any faster, they would cramp. So I had to slow things down, even though I otherwise felt good and had plenty of gas in the tank. I knew electrolytes weren't the issue because I was taking in plenty, and it seemed evident to me that fatigue was the issue. I tend to wear light weight running shoes in races, and I think my legs just can't take the pounding. I am pretty methodical in my training, and I have suffered from cramps even when I was running well within my fitness level. I have never cramped or felt similar sensations in half marathon races or 23 mile training runs in the heat. I wonder if switching to more cushioned shoes like I use in training would help. They are heavier, but if they helped with cramping, that would be worthwhile to me.

Incidentally, are there are any athletic events where you see cramps in the arms, e.g. biceps, triceps?

Anyway, keep up the interesting work and thanks for making it more accessible to the masses than some of the scholarly work I see out there.

Anonymous said...

I've recently stumbled upon your blog and it's great! I'm a layman so please excuse the "unscientic" questions.
1) In your article you mention that cramping occurs in the muscles that are associated with the work that is being performed. I am a relatively competitive road & MTB cyclist and have in the past experienced cramping at times in my forearms & fingers, so much so that my fingers have literally clamped to my bar! I also don't then necessarily cramp in my legs. Any hypothesis on why would this happen?
2) Has lactic acid build-up, where the muscles are unable to utilise the fuel in that form any more, anything to do with cramping?
3) Could an excess of caffeine (diuretic) affect cramping?
4) Will regular sports massages (also deep tisue) have any effect on cramp prevention / alleviation?

Thanks for the interesting science.

Ross Tucker and Jonathan Dugas said...

HI to Anonymous and to Russell

Thanks for the comments, glad to have you!

To respond to Anonymous, interesting one that. I think the fact that you recognized the cramp coming on and then could prevent it from ever developing by simply slowing down is an indication in itself that electrolytes are not to blame - how could you 'consciously' suddenly raise your electrolytes by slowing down? So that suggests right away that it's something related to muscle function and work.

As for the shoes - good question. I must confess I don't know of any studies that have even examined the influence of cushioned shoes on fatigue. They have looked at loading and impact forces and the like, finding that cushioning reduces them, but how this then relates to fatigue, I don't know from any concrete evidence. So we can't even infer the answer indirectly...

My gut tells me that a cushioned shoe would reduce the fatigue component in the muscle, based on a mixture of personal experience and a slight 'educated guess' - I suspect that with additional cushioning, you might reduce the eccentric work of the muscle when landing, and this might make the difference.

The other, of course, is regular strength training - train the muscle to resist fatigue by specifically loading it.

Russell, the answer to your question follows in a separate reply.

Thanks again!

Ross Tucker and Jonathan Dugas said...

Hi Russell

As promised the answer to your question. But first, I neglected to answer Anonymous' second question about events where you
have cramping in the arms...partly because you provide half that answer!

So we'll go through them one by one...

1. Cramping in the arms is not all that uncommon during cycling, especially mountain biking. I've in fact experienced it myself, and it's because you are actually using those muscles in a very specific and local contraction. The arms and especially the forearms and fingers are working 'isometrically' - this means that are doing static contractions, gripping the handlebars for prolonged periods.

Try this - point your foot and toes down as forcefully as possible for about 2 minutes - you'll feel pretty close to cramp by the end! The reason is that you're putting yourself in the perfect position for cramp - sustained muscle contraction in a shortened position. Now, with the forearms and fingers, it's not quite the same ideal position, but the principle is the same - a sustained contraction causes cramp quite easily. It's actually quite common - all the guys I ride with have the same problem. The remedy, of course, is to make sure you take every chance you get to loosen up your hands, relieve the contraction, stretch your fingers etc.

2. Highly unlikely, in fact, I'd say with about 99% certainty that it's not related in any way. This is another huge myth in the exercise sciences, and maybe the topic of a series in the near future!! But no, lactate is not responsible, and we know this for a number of reasons, but the two main ones are that there are people who can't actually produce lactate (they have a disease that prevents it) and they cramp more than most.

And secondly, you cramp in the marathon at the end of the race when the lactate levels are very low, and not in the final 10 minutes of a 10km race when the lactate levels are much higher. So it's the fatigue that is more responsible, not lactate.

3. Not that I know of - never been shown in any studies of exercise. Perhaps in clinical situations, where you might have an overdose, but that is not an area I know that much about - if we have any clinicians who do, please let us know. But I can say with certainty that no studies of exercise have found this association.

4. Again, excellent question. And here again, there are no controlled research studies that say either yes or no. So it's impossible to say that it does or doesn't. You would need a study where some people receive regular massages and therapy, and others do not, and then both groups are made to exercise hard enough to get cramp. But there are so many problems with this study design - you can't guarantee that your two groups will even cramp, or that they are equally likely to cramp, and of course there is no control group that takes out the placebo effect!

So this is a study I doubt we'll see, and rather, we have to limit ourselves to what are called case series, and the good old anecdote!

Again, my gut feel is probably that they don't, because of the nature of the cramp - if it is fatigue related, then a massage the day or two before is unlikely to have much effect. Massage while the cramp is happening does have an effect, however, and perhaps regular massage would work - who knows? This is a great case where people should find what works for them and then go with it! If it's a false effect, a placebo effect - that doesn't really matter!

Hope all this helps - your questions, which you called "unscientific" are in fact very challenging! I can't even answer half of them with science, and have been relegated to "unscientific" answers! SO thanks a lot, and keep them coming!


Anonymous said...

Hi Ross & Jonathan

I'm a loyal reader of your blog which posts many note worthy and insightful knowledge and discussion.

I came across the below study which validates the theory of salt in preventing and treating cramp caused by excessive sweating.

The Role of Sodium in `Heat Cramping'
Eichner, E. Randy1
Sports Medicine, Volume 37, Numbers 4-5, 2007 , pp. 368-370(3)


`Heat cramping' is defined here as severe, spreading, sustained, sharply painful muscle contractions that can sideline athletes. Not all cramps are alike, but three lines of evidence suggest heat cramping is caused by `salty sweating', specifically by the triad of salt loss, fluid loss and muscle fatigue. The first line of evidence is historical. Dating back 100 years, heat cramping in industrial workers was alleviated by saline, and in a self-experiment, salt depletion provoked muscle cramping. The second line of evidence is from field studies of athletes. In tennis and football alike, heat-crampers tend to be salty sweaters. Some evidence also suggests that triathletes who cramp may lose more salt during the race than peers who do not cramp. The third line of evidence is practical experience with therapy and prevention. Intravenous saline can reverse heat cramping, and more salt in the diet and in sports drinks can help prevent heat cramping. For heat cramping, the solution is saline.

Ross Tucker and Jonathan Dugas said...

Dear Half-timer

Thank you for your loyal readership, we're pleased you enjoy our content!

To respond, Randy Eichner, the author of that article, is one of Gatorade's biggest advocates - in fact, in our first post in this series on Muscle cramps, we actually were referring to him when we spoke of the issue of "salty sweaters"! We said then, which I repeat now, that this issue of salty sweaters is complete nonsense.

In fact, the afore-mentioned Randy Eichner stood up at a conference recently, spoke about salty sweaters, and when he was challenged by one of the delegates (Schwellnus) to define what a salty sweater was, he simply could not - the fact of the matter is that these guys don't have evidence to support their case.

So what this article represents is NOT RESEARCH. Let me stress that point again - this article is NOT research. In fact, there is not a shred of controlled evidence in it - only anecdotes and theories, never tested.

So for example, when Eichner writes that "more salt in the diet and in sports drinks can help prevent heat cramping" he is talking completely out of turn - this evidence does not exist.

As we've pointed out, this is the big problem in this area - nobody has proper, controlled science to back up their models, because no one has ever studied the administration of salt to crampers in a controlled setting. Of course people respond when they receive a saline infusion - by that time, they're lying down in the medical tent and their fatigued muscles are relaxing! So this confounding factor is never controlled for!

I think that what we will do is look at these 'studies' and in our final post on this topic, just have a look at them. What we presented in Part II of this series, is about the only evidence of the actual sodium levels of crampers.

And let me repeat what hat study found:

People who cramp have the same sodium levels as non-crampers
People who cramp have the same fluid loss as non-crampers
People who cramp have the same temperature as non-crampers.

And Randy Eichner did not mention any of these studies in his review, because they disagree with him.

But we'll discuss this evidence at length tomorrow!

Thanks for the comments!


Anonymous said...

Looking forward to your upcoming posts. I assume you will tackle the question of what a marathon runner (or any other athlete) who regularly experiences cramps should do. It sounds like weight training for the problematic muscle would be a good idea.

Anonymous said...

Hey Ross and Jonathan,
Thank you for your insightful article.

If muscle cramps are indeed caused by fatigue, is it possible for an athlete to train to minimize the probability of cramping in competition?

Also, in the case of cyclists, could improper pedaling technique (excessive "ankling", for example) or poor bike fit contribute to cramping in the calves?

Anonymous said...

so what is fatigue? In the race context it is performance above and beyond training. This does not answer the question of what is the physiological cause of alteration in the reflexes. How does performance beyond one's trained capacity produce the effect?

Anonymous said...

Hi Ross/Jonathon,

Unfortunately, but timely so, I just suffered a severe cramp in the night. I believe it is related to too much drinking, but not Gatorade.

Friday night involved perhaps a little too much alcohol, and Saturday morning, I awoke to severe pain in my calf (luckily I knew to stretch the calf, and not point the toes). It's still a little sore today (Monday afternoon).

After an extensive survey of my colleagues (2), they anecdotally concured that there is a strong correlation between alcohol intake, and nocturnal muscle cramps.

Any room in the "muscle fatigue" theory of muscle cramp for alcohol-induced muscle cramps?

Painfully yours,

Ross Tucker and Jonathan Dugas said...

In response to Brian's comment a few posts up. . .

First, applying the Law of Specificity will help ensure that you do not cramp on the day. Simply put, you practice like you play, and so if you complete all your training sessions at 60% and race at 85%, you have violated this law.

In short you will have made excellent adaptations to exercising at 60%, but few (if any) adaptations to exercising at 85%. Therefore when race day arrives and you hammer it at 85%, this represents a stress for which your body is poorly prepared. An early onset of fatigue results, and with that comes all the associated things like cramps and poor performance.

Second, pedaling technique or poor bike set up could certainly predispose you to cramping, especially if your set up leaves your hamstrings/calves in a shortened position for long periods of time as described in Part III of this series.

On the pedaling technique issue, I have seen this in guys who try to replicate Armstrong's high cadence "circular" style. They pull up using their hamstrings, which first shortens them more and second fatigues them faster, resulting in cramps after some time.

So watch that bike fit and set up, and stay away from extreme ends of the spectrum when it comes to altering your technique.

Kind Regards,

Anonymous said...

Hello, Continued research on this important subject is appreciated. My comments are anecdotal.

Childhood craving for salt and bananas. Lifetime of near-OCD devotion to strenuous and endurance sports; including football, basketball, volley ball, distance running, distance bicycling, tournament tennis. Fanatical fitness workouts/superior conditioning.

Chronic cramps.

Med resident tennis partner says potassium chloride ion needed. Regularly supplemented with salt and potassium, and did not cramp again for 10 years.

A fair number of cramp episodes since when fail to supplement first. Every cramping episode subsides essentially immediately when I chew some potassium and salt.

Ross Tucker and Jonathan Dugas said...

Hi Anonymous, and thanks for sharing your story with us here.

Your anecdote helps illustrate an important point, namely that if you find something that appears to work for you, and it does not cause any harm or negative side effects, then bugger the science and keep on taking it!

We have stated this before and I will say it again here---we can have all the scientific data in the world from well-controlled lab studies, and still something entirely contrary might work for some individual(s). And when that is the case, they must continue to practice that thing as clearly it has some positive effect.

The one point I would like to make, though, is that physiologically we cannot explain how your supplements prevent cramping before you even (or as you) swallow them. This is because you still must empty the contents of your stomach and then absorb those contents from your gut. Therefore when you swallow them nothing has yet changed in your body, and it won't change until you get it past the stomach and the gut. So you might be experiencing a placebo effect of the supplements.

However, the placebo effect is a real effect, and again, I cannot stress this enough, if it works for you, there is no good reason to stop using this supplement. The science may say that it should not have an effect, but, again, if it works for you, keep doing it.

Best of luck with your future sports endeavors and thanks for joining the discussion here at The Science of Sport!

Kind Regards,

Unknown said...

Probably way too late to post this, but this interesting series was referenced on another forum yesterday (April 20, 2008) as a good source for science on cramping and it is. Still, I have a few questions and reflections after working through the series.

In the conclusion, you say people who cramp have the same sodium levels as those who do not. In fact, as you summarize in earlier installments of the series, people who cramp have lower sodium levels. I have worked my way through your explanations of why such lower sodium levels do not point to dehydration and why sports drinks would not address such low sodium levels. Nevertheless, this seems an interesting, and potentially significant difference.

Much of your series seemed aimed at disproving the whole sports-drink hype, and I'm sympathetic to that. I've never known anyone who solved their cramping problem by drinking Gatorade or another sports drink. That said, I'm still intrigued by the extra weight loss among crampers. You said it can't be fluid loss, but must be calorie burning. Perhaps. But this extra weight loss seems another important distinguishing factor for crampers, perhaps pointing to something having to do with sweating.

The higher magnesium levels in crampers is another interesting factor, not understood, that seems to balance an exclusive focus on fatigue and mis-firing.

You argue toward the end that the electolyte/dehydration theories are disproven by the fact that stretching relieves cramping. But it seems logical to me that various physiological factors that are indicated, at least indirectly, by the lower sodium, extra loss of weight, high mag. levels (note: I am not saying lack of Gatorade or the equivalent!) might contribute to the loss of control of muscles, but that -- with the onset of cramps -- stretching might help restore such control, at least partially. In my experience, stretching helps a little for a little while, but once my muscles cramp, it is days or weeks before they are back to normal.

I have cramped a lot, particularly in race situations (I'm a cyclist), but also sometimes in very easy rides (easy defined by power and heartrate). I have no doubt that fatigue is an important factor, but the one-sided emphasis on that (and on disproving the sport drink companies) seems to obstruct openness to other dimensions of the problem.

Finally, a theme that comes up multiple times in the series is that the electolyte theory would not account for why cramping occurs particularly in certain muscle groups. Actually, it is possible, is it not, that some kind of imbalances might make one susceptable to cramping, but that susceptability would only be activated in muscles that were fatigued? Why not be open to a mixed model of some kind?

One thing in my case that might point to multiple factors, including systemic imbalances, as important is that I have had post-exercise cramping in muscle groups that were not heavily fatigued in exercise. After a hard race yesterday, my hand -- the palm -- was cramping at dinner. One might theorize that my right hand got more of a workout in the race. I can just say that I find that unlikely, and I've had other non-related muscles cramp (albeit less often) post exercise.

I have no ax to grind here. I am at the end of my rope in terms of my own cramping issue. I train in a focused, disciplined way with someone whom I think is a good coach (and others do too). I still have cramps, including every single major out of town competition I've been in (I'd be great for repeatability in a study). I am impressed that some athletes with problems similar to mine have reported significant reductions in cramping with more extreme and varied electrolyte supplements than in a typical sports drink. So far that regime (I've tried everything), has not worked -- nor has stretching, use of muscle compression products, competition-specific training (reproducing stresses of event), more focused hydration (topic of another series, I know), etc.

Sorry for the long post. Thank you for so generously sharing your expertise. My challenging response comes from my desparation for answers to what seems a still partially understood phenomenon. I agree that the marketing hype has obscured progress on this, but also think that much remains unclear. I'm very grateful for any additional help or clarity that you can provide if you see this.

David C from New York

Ross Tucker and Jonathan Dugas said...

Hi David

Thanks for the comments and questions. I don't have time right now to work through the full answers, but will make one point:

That is, crampers actually lost less weight, not more. So your question revolves around EXTRA weight loss in crampers - it's the other way around, because studies have shown that crampers lose less than non-crampers, not more. You'll see that in both tables in Part II of this series.

So that's one issue - unless I'm missing something. I'll try to get to the other points at some time later, when I have more time!


Anonymous said...


Thanks for an interesting and informative series. If you're still monitoring these posts: I'm curious if there's evidence tying cramping to air temperature.

Anecdotally I have a clear connection. Through the winter I've been doing about two long bicycle rides a month in the 160 to 260 km range. Some of these were fairly intense, but I had no trouble with cramping until last week when the temperature finally climbed over 25 degrees C. This cramping occurred on an easier ride and one where my fitness level was better than on the earlier rides.

I know that a lone data point isn't very meaningful, but I agree with David in that there may be additional factors besides fatigue at work in cramping.

Jonathan (also)

The Cycling Addiction said...

Thank you for this article on cramping and responding to some of my questions a few weeks ago on cyclingforums.com. I wrote my expereince this past weekend with severe cramps related to muscle fatigue and linked this article on my blog for further reference.



Ron Castia said...

Sorry, but from experience of being a chronic cramper who has solved the problem, it is most certainly electrolytes.
Lack of or a shortage of electrolytes increases the fatigue of the muscles being used. Add in poor fit on the bike and you will surely get muscle cramps.
I have been able to come back and finish well in a race after severe cramps using two things. Endurolytes by Hammer Nutrition, and an increase in intensity to get the heart rate and blood flow up.
Meaning, I take the Endurolytes then attack. Cramps go away.

The fact that I can attack during or just after a severe cramp and clean it out throws the fatigue theory right out the window.

Ross Tucker and Jonathan Dugas said...

Hi Nome

Unfortunately, the only problem with your theory is that when you have these cramps, your electrolyte levels are probably not low! So your entire model is predicated on the assumption that low electrolytes exist to begin with, and the data suggest that this is not the case!

So that minor detail aside, the next problem is that you yourself don't believe your own model, because you attribute your recovery to an increase in heart rate and blood flow, but that negates the electrolyte effect. There is no evidence that the heart enables the legs to work harder - it's the other way around. When the legs work harder (that is, you activate more muscle), then your heart rate goes up.

That said, your anecdotal account is interesting, because these kinds of anecdotes are worthy of taking into account. Now, I'd be interested to know how an increase in intensity would affect the brain's regulation of muscle. Because if you read the article, you see that the reflex control of the muscle is key to the cause of cramp.

Now, it's feasible that an increase in intensity (when you attack) is also able to impact on that reflex control, and so that's something worth considering. Then of course, there is the enormous placebo effect that exists when people believe they are doing something to help them, and that can't be discounted. I suspect that if a friend of yours gave you sugar water instead of Hammer Products,your problems would also go away. You might consider that as a fun little experiment, where a friend of yours gets to fill your water bottle with either an electrolyte/sugar drink, or just sugar, and see which works. I'll bet that both will work...


The Cycling Addiction said...

Nome, I wouldn't want to speculate what others are experiencing or not. What may work or what may not, but I do know that this article has helped me understand what I already instinctively suspected about the cramps in my situation.

This is a culmination of 25 years of high level of competitive training in an anaerobic event and knowing what it feels like to over reach and feel fatigued, but I do not want to rely totally on observations. I would like to have a reasonable scientific explanation and look for a solution.

My observations of myself and others may differ slightly concerning fatigue, but one of the first signs for me personally is a sensitive heartrate with very little stimulation and the biggest sign is a swollen lymph gland under one of my arms. I had experienced both of these before these rides and though I hoped for a good performance day could predict a potential bad day early in the event. My cramps occurred later in the training events while riding with others that are advanced above my level and were pushing a hard pace.

The article provided here on cramping helps me confirm by science what I had suspected to be the case. For me I want to solve the problem quickly and not make guesses at what I think might be the solution.

Unknown said...

Ross and Jonathan,

I like your articles, especially your ability to approach the problem of cramping with scientific evidence. As a medical student I am able to completely understand the scientific findings regarding the increased muscle contraction signalling. However, my question is this: What do we do about it?

I, like most other athletes, have a problem of cramping that is not solved by throwing back Endurolytes or any kind of liquid in a race. So, if I am cramping by an increased signalling in muscle contraction, what do I do about it before and during the race? Is this something that can be semi-fixed in a race once it has already happened (by letting my legs relax on a downhil) or what?

I look forward to your advice.


Unknown said...

Ross and Jonathan,

One more thing to add.... I am an avid before-race stretcher (although I can always stretch more), BUT is there anything I can do during a race?


Ross Tucker and Jonathan Dugas said...

Hi Chris, and thanks for your message here.

Regarding any maneuver you can do during the race to help with cramps. . .well, that is a tough one!

However, the one thing we notice is that crampers tend to be people that "out race" their training. The best way I can explain this is the athlete who has trained for a 3:40 marathon, but gets so excited and swept up by the excitement at the start that he decides to run at 3:00 hour pace.

Because he is well-trained, he can do this for at least 21 km or more, but then the fatigue component becomes quite prominent and the cramps set in.

So adopting an appropriate pacing strategy is certainly something you can do during the race. The trick is the "appropriate" part, as that will be individual to each person's training, talent, and fitness.

One thing I would also suggest is not just pre-race stretching, but rather a regular stretching program that targets the muscles in which you cramp. By regular I mean stretching 2-3 times per day a few days per week. This approach helps in those individuals who cramp in the middle of the night.

Good luck!

Kind Regards,

Anonymous said...

Hello Ross and Jonathan,

Thanks a lot for your blog, it is not easy to find reliable source of information in the rubbish ladden cyberspace.

Unfortunately, coaching is overloaded by lockeroom anecdotal evidence so your very valuable series contributes to evidence-based practice finding its way into sport and exercise - long overdue IMHO.

I fully agree with your views on hydration and cramps, and I read your explanation of the neural theory in exercise-induced muscle cramps (EIMC)with great interest.

In one of the articles you mentioned problems in studying cramps phenomenon due difficulties in reproducing them in the lab environment.

In clinical setting (I'm a physio) I observe cramping very often in people with weak muscles that are pathologically shortened through non-use esp. in the elderly. The above example would correlate well with the neural theory - shortened muscle = nonstimulated GTOs. So maybe there you can find subjects for further research...

However, I would like to bring to the fore a metabolic aspect of local muscular fatigue which I think may contribute to the development of EIMCs. I believe that, the molecular energy of ATP is required for both contraction AND relaxation of the muscle. So to unbind the actine-myosin complex ATP energy is needed in the working muscle but if the muscle fibres are ATP depleted than the relaxation would not occur and through continues neuro stimulation the muscle spirals into tetanic contracture.

Similar thing occurs in rigor mortis...

Stretching of the cramped muscle is like a manual overdrive to open otherwise automatic sliding door - something gotta give so I believe the intense pain of stretching a cramped muscle comes from physically ripping the bridges of actine-myosine complexes apart, rather than further stimulation of the muscle spindle.

Long lasting muscle soreness after stretch like this is suggestive of muscle microtrauma.

Metabolic theory would also account for frequent return of the cramp if the stretch position is released prematurely and/or the causative activity is recommenced.

I would really appreciate your input.

Best Regards


Anonymous said...

Dear All,

I have followed Schwellnus's research since my Uni days and have found it to be spot on.

From 2003-2007 I worked as S&C Cocah for the Queensland U18 AFL team. We played most of our 'big matches' in Victoria. Queensland has hard fields (less rain) while Victoria has very soft fields (lots of rain).

During my first game in Victoria most of the team experienced cramps, mainly in the calves. Knowing the owrk of Schwellnus, and figuring the calves were working harder on the softer grounds we introduced a static stretching protocol at 1/4 and 1/2 time. After 2-3 games, once the calves had adapted to the work load, no stretching was required. Cramping problem solved.

Unfortunately, if a player was introduced to the squad later in the season, and I relaxed on the stretching protocol, he would inevitably cramp.


Anonymous said...

First, thanks for your time with this posting.

Second, maybe I've missed this, but what would be the appropriate steps to take for one who cramps if this were the cause? Simply stretching and training properly or would there be more to it?

JKP said...

Great article. Assuming this theory is correct, what is the "intervention" a cramp-sufferer should take to stop a waive of cramps? I've suffered three episodes of severe crapping in the last few months, the most recent last night, when, after playing 2 hrs of "A-level" singles tennis in the morning, and then being on my feet coninuously until 10pm, I endured 5 periods of severe cramping of all thigh muscles over a 2.5 hr period, starting in one leg, and then occuring in both. The last period lasted ~15 minutes, during which I sweated profusely and could only bear the pain by standing with legs spread to stretch the inner thigh muscles, where cramping pain was greatest. It's interesting to know the cause, but knowing the "cure" would be even more helpful. Thanks!

Unknown said...

WOW! I can't beleive I never came across your information before!! I'm a 49 year old Road & MTB racer. I have been racing for 7 years now and I'm the joke of the team, because of my cramping issues! I have tried: Sportegs, Endurolites, and was ready to try pickle juice, thats how desperate I am!
My cramping always occurs in my inner thighs, and for some races that I have done many years in a row, at the same time and place on the race course.
If I undestand you right, I need to either : train harder or race easier and forget all supplements right??


Unknown said...

I'd say, yes, train harder, race easier, but also attend to things like fuel and cooling, since both also can affect fatigue, which seems to be the main prompter of cramps. I've found that close attention to fueling, including on training rides throughout my cycle, made me much less prone to cramping.


Anonymous said...

Hi Ross & Jonathan, Thank you for sharing this information. I have been searching for answers as a lay man. Muscular cramps of the calves are common in the game of cricket especially in hot conditions like the sub continent. But most cricket coaches still believe that this is a result of poor hydration, eating too much cooked food etc and other new age nonsense. Do you have a forum?

Anonymous said...

I was very interested in this article and the theory around fatigue and muscle cramping. My question is does the muscle cramping associate with fatigue occur immediately following an event or is it possible that as a result of increased physical activity training , the fatigue on the muscle can have long lasting repercusions that is teh cramping may occur a few day safter the activity when attempting to exercise. I hope this question is clear. Thanks

Frank Day said...

Here are a couple of problems I see with the analysis.

First, what is meant by fatigue? We have all seen athletes exercise themselves to exhaustion yet nary a cramp can be seen. While I occasionally get cramps in bed. So, while fatigue might be present in some instances this doesn't explain the muscle cramps I (an many others) get in bed at night not associated with any fatigue.

Second, looking at electrolytes generally just looks at the extra cellular fluid electrolytes when, if electrolytes are the source, it is likely it is due to a deficiency in some intracellular electrolyte or some problem in the intracellular/extracellular balance (perhaps accompanied by some increased sensitivity from "fatigue"). If this is the case, the problem for the athlete, who is experiencing cramps, comes in trying to correct any imbalance while continuing to exercise. Just getting intracellular electrolytes into the extracellular fluid doesn't get them into the cells and could make any membrane imbalances actually worse.

Anyhow, I suspect this issue has multiple different "causes" and each "cause" is multifactorial such that it is possible that everyone is "right" to some degree and no one explanation explains every instance.

Anonymous said...

I believe you are falling into the same trap as the electrolyte cramp group by simplifying a complex issue. I would venture that both electrolyte imbalances and muscular fatigue are players in cramping depending on the situation. Moreover, you use a lot of data to support the idea that may be entirely artifact ie BW loss or serum electrolyte concentrations. If you want to show that electrolyte concentration isn't involved in muscle cramping then provide evidence that no electrolyte differences are observed in the cramping muscles. Serum concentration are far removed from the cramping muscle and may be meaningless. No mentioned at all(unless I missed it) was given to muscle damage during exercise. I would guess that this is a player as well since tears to muscle would alter intracellular Na/K concentrations and make a muscle more prone to cramping.

I would also purpose the length of exercise is important to your analysis. I don't know that marathoners are the best subjects. The event isn't long enough to ensure that all subjects are sufficiently dehydrated to induce electrolyte related cramping. Yet you then claim that electrolytes have nothing to do with cramping when in fact it maybe a subject or methodology problem.

Finally this is purely my personal anecdotal evidence,so take it as you may. I cramp under these conditions only: long endurances events lasting 4+hrs, in hot conditions (temp>85degrees), and occassional during the night but only when training in really hot periods of the summer, and I can't remember ever cramping in relation severe fatigue. I have a excessive sweat rate(over 5 lb/hr). That said, I've all but stopped my cramping issues by through electrolyte replacement something you are suggesting athletes avoid.

While I can't state that muscular fatigue has nothing to do with cramping, I believe your claims that cramping has nothing to do with electrolytes is unwarranted. The issue is more complex than you suggest and your all or none analysis too simplistic. This subject needs more and better research before the electrolyte and/or muscle fatigue ideas are rebuked.

Carlton Newman said...

In 1981 I attended a lecture by the world renown herbalist Maria Treben. She was just introducing her book to America entitled "Health Through God's Pharmacy" as it had already sold 2 million copies in Europe.

When she started talking about Common Club Moss (Lycopodium clavatum) and how it relieved muscle cramps and spasms in seconds my ears perked up because almost nightly I would get foot or leg cramps. I would often be awake for 1/2 hour or more trying to get the cramp to relax and then when I went back to bed the cramp would come back and I would repeat the process.

After the lecture I bought some common club moss bulk herb tea and put the herb in a pillow as she recommended. Whenever I got a cramp I would place the herb pillow over the cramp (like you would a hot pad or ice bag) and immediately I could feel the muscle begin to relax. In a minute or so the cramp was gone and with it all stiffness, soreness and pain. I would keep the pillow in bed with me and fall asleep, the cramp never returned and I got a great nights rest. Even intense Charley Horse cramps were no match for this herb, and it even worked on my hiccups.

In 2002 I got the idea of helping others who suffered from cramps and spasms. It even works on menstrual cramps and infant colic. It works on any voluntary or involuntary muscle of the body regardless of the cause (except for cramps caused by nerve damage such as a pinched nerve). You can read more about it at my website: http://www.zapakramp.byregion.net.

I hope this helps some of you as it has me.

Carlton Newman

Marius said...

I just don't know anymore. My cramping seems to differ from the other folks here in the sense that when i cramp it is always hot, i never cramp when it is cool, and mostly I cramp after a race. My cramping is not specific to the muscles i use for cycling for instance. I will cramp in my fingers, upper back, neck, ribs. really doesnt matter. Mostly when it starts it will quickly spread to full body cramping. i have to stretch the affected area fairly fast to prevent any more cramping.

When i cramp while cycling it allways starts in the same leg only. i can feel the twitch and when it starts it can quickly get out of control.

I sometimes feel the twitch in my fingers or ribs as well before it starts.

The muscle that normally starts is not the hamstring or the quads. it is a small sinew between the two on the inside of the leg about mid way.

I have gotten cramp at 30 minutes into a race when not even going very hard, but mostly after about 4 hours and when it is very hot.

The imbalance theory makes the most sense to me in my case as it is normally most of my muscle groups that cramp, not just the muscles being worked the hardest, as is the case with cycling where your hamstring and quads are working the hardest.

I have found though that stretching before and after does seem to help, but not always.

I am trying a home made concoction of multodextrin and salt and will see how that goes. i aslo drink a lot of fluid (almost double) compared to the other people i race with and are on the same pace as i am.

Can you guys maybe enlighten me on subjects such as saltloading or something similar maybe as i deduct from the trials that the guys that cramped had less salt in their blood which indicates adequate or over-hydration. Would adding salt not then equalise things out ?

Piilani Schneider said...

I have a 15 year old competitive kayaker. She cramps in the first 500 meters of a 2000 meter race. She stops, than pushes herself. Sometimes the cramping will go away allowing her to finish the race strong. However, she jumps out ahead of the pack only to finish second due to her cramping. This is becoming a pattern & very discouraging for someone as competitive as she is.
Is a heat patch effective in this situation?
Thankyou for emailing me your reply as I'm not sure I know how to find your blog again? Internet illiterate :o0

Unknown said...

Hi Ross and Jonathan
A little late to comment on the cramps series! Ross I recently heard your talk at the sports science centre and looked you up on the internet afterwards- only to be very happily surprised to find your and Joanthan's blog - now I am an avid reader and following the fatigue series.thank you both for your selfless sharing.

On cramps and my question (contribution). In the recent Winelands marathon I cramped badly from around 26km onwards. Being my first in many years and having a number of my club mates in front and behind me I was determined to continue no matter what. So I did what runners do: I stretched, I walked, I sat down at times, I took off my running shoes and tried running in socks (felt better for part of the run), put them back on etc. BUT I also walked and ran BACKWARDS, including downhill, successfully, over many stretches (I would turn around after a while and try running normally again). THE POINT is when I was running backwards I suffered no cramps (or the cramps that was there did not worsen). point for the muscle reflex model since I was not using my contracting my calves in the way that was leading to cramps? Running backwards is odd and does not make the km go very fast so I always tried to run normally.
A QUESTION as well: I had done enough training to last up to 24km at a moderate pace so should not have expected to cramp so early - I can understand about cramping later as runners tend to do - why so early in my case? I took enough fluids as normal including a gell by then and a rehidrate.
Thanks very much.
Mark Jacobs

Beau said...

I realize I am way behind on this, but I have a question. Your solution to the cramp through the use of passive stretching seems to take a large period of time to engage. Would the time period be shortened if not just passively stretching but actively engaging the opposing muscles? So if your calf is cramping would you not get a more immediate response of muscle release if you fully activated the anterior tibialis? I read a lot about this in studying the Mattes Method of Active Isolated Stretching. If I'm not mistaken, if you fully engage the full range of motion with a muscle, the opposing muscle must relax. Just curious as to what you've seen.

Anonymous said...

Great article. I am frequent cramper and personal experience supports the fatigue theory. I have had very positive reaction to taking Calcium tablets (with Magnizium) as I feel a cramp coming on. It has the magical effect of 'melting' the cramp temporarily. The cramp will return after a few minutes though. I suppose it could be placibo affect as I may simply slow down as I take the chewable calcium. Could it be that calcium does have a favorable impact?