Saturday, December 20, 2008

Electrolytes and Muscle Cramps

I got a real kick out of this cartoon, especially given my recent 4-part series on hydration. I think Monty is spot on here—most of us don’t know what electrolytes are but believe we must get them during exercise or something bad is going to happen. The most common belief is that we will experience muscle cramps if we run low on electrolytes. What actually happens during exercise is that the concentration of electrolytes increases since far more body fluid is lost as sweat. Sweat is hypotonic, meaning that the concentration of such stuff as sodium, magnesium, etc in it is far less than what the normal concentration is in the body. And the body appears to operate based on concentrations, not absolute amounts. Sports drink marketing has led us to believe that it's absolute amounts. The following is a previous post from my blog on the subject of muscle cramps…

In the spring I get a lot of email from athletes describing how they just did their first races of the season and were going great until a cramp came on. Should they eat more bananas or take in sodium while exercising, is the most common question.

That cramps are more common in the first races of the year and not in the late season probably tells us something. No matter how hard you've been training in the spring the workouts are not as hard as the races are. The body simply isn't in race shape yet. By the end of the season the body has adapted to the stresses of racing and is less inclined to cramping.

But for a few athletes the problem continues throughout the year. There is no more perplexing problem for these athletes than their susceptibility to cramping. Muscles seem to knot up at the worst possible times during their important and hard-fought competitions.

The real problem is that no one really knows what causes cramps. There are just theories. The most popular ones are that muscle cramps result from dehydration or electrolyte imbalances. These arguments seem to make sense—at least on the surface. Cramps seem to be more common in the heat when low body-fluid levels and the possible decrease in body salts are likely to occur.

But the research doesn’t always support these explanations. For example, in the mid-1980s 82 male runners were tested before and after a marathon for certain blood parameters considered likely causes of muscle cramps. Fifteen of the runners experienced cramps after 18 miles of the race. There was no difference, either before or after the race, in terms of blood levels of sodium, potassium, bicarbonate, hemoglobin or hematocrit. There were also no differences in blood volume, a marker of dehydration, between the crampers and the non-crampers. Nor were there any significant differences in the way the two groups trained.

It’s interesting to note that athletes are not the only people who experience muscle cramping. Workers in occupations that require chronic use of a muscle, especially one that crosses two joints, but don’t sweat profusely as athletes do, are also susceptible. A good example is musicians who are known to cramp in the hands and arms.

So if it isn’t dehydration or electrolyte imbalance, what causes cramping? Other theories are emerging. One is that poor posture or inefficient biomechanics are a cause. Poor movement patterns may cause a disturbance in the activity of the Golgi tendon organs. These are “strain gauges” built into the tendon to prevent muscle tears. When activated, these organs cause the threatened muscle to relax while stimulating the antagonistic muscle—the one that moves the joint in the opposite way—to fire. There may be some quirk of body mechanics that upsets a Golgi device and sets off the cramping pattern.

If this is the cause, prevention may involve improving biomechanics, and regular stretching and strengthening of muscles that seem to cramp along with their antagonistic muscles.

Another theory is that they result from burning protein for fuel in the absence of readily available carbohydrate. In fact, one study supports such a notion. In this research, muscle cramps occurred in subjects who reached the highest levels of ammonia release during exercise. High ammonia levels indicate that protein is being used to fuel the muscles during exercise. This may indicate a need for greater carbohydrate stores before, and better replacement of those stores during intense and long-lasting exercise.

When you feel a cramp coming on there are two possible ways to deal with it. One is to reduce the intensity and slow down—not a popular option in an important race. Another is to alternately stretch and relax the effected muscle group while continuing to move. This is difficult if not impossible to do in some sports such as running and with certain muscles. Actually there is a third option which some athletes swear by—pinching the upper lip. Strange, but true.


At December 20, 2008 7:26 PM , Blogger Mama Simmons said...

That's interesting about the ammonia release during exercise. I've smelled that on myself before (not regularly, but it's happened) but never knew what it was. Thanks for the info!

At December 21, 2008 8:05 PM , Blogger Jesse said...

Glad to have found your blog - I'm a big fan.

I never used to get muscle cramps, but as I progressed in endurance sports, I pushed my body harder and have noticed them in two situations...

First, running fast for a longer distances in cool weather (~50F), if I spill water on my torso at aid stations I get pretty bad side stiches.

Second (and this only happened once), when transitioning from a very hard bike effort to a hard run effort (Olympic Tri), I got some pretty bad cramps that took several miles to go away.

At December 22, 2008 2:57 PM , Blogger jonovision_man said...

Your article is spot on...

I remember doing an early-season mountain bike race which ended in a pretty serious climb (Paris to Ancaster, an Ontario classic!)

As I started the last climb, about 2h30 into the race, I cramped up horribly - we're talking lying on the ground writhing... I looked over and there was not one, but TWO other people doing the exact same thing, all of us within about 20 feet of each other.

I've never seen anything quite like it before or since!

Early spring, pushing yourself for almost 3 hours when you haven't been on the bike more than a half dozen times since the previous fall... bad mojo! I could try to blame electrolytes, but I think "undertraining" is far more likely... for all 3 of us crampers! :)

At December 22, 2008 4:49 PM , Anonymous Anonymous said...

Here's a direct link to the online version of the Monty cartoon:

At December 28, 2008 12:11 AM , Blogger Morten Liebach said...

Given that the amount of electrolytes lost through sweating is dependent on acclimatisation to heat (ie. you loose more electrolytes when you're not used to sweating a lot in the heat, but as you get used to the heat the electrolyte loss gets smaller for the same sweat rate) couldn't it be that at the first race(s) coming out of the cold winter you're loosing more electrolytes and therefore cramping more. As you get more acustomed to the heat you loose less electrolytes, leading to less cramping.

But that doesn't explain it for an athlete used to training indoors on a turbotrainer og taking spinning classes during the winter, but might point to a solution for those with the problem.

Personally I've never really cramped up during a race, so I guess I'm just lucky. But I also do indoor cycling through the winter.

At December 28, 2008 6:42 AM , Blogger Joe Friel said...

Hi Morten--Thanks for your comment. While it's not certain what causes cramps, one thing has been demonstrated repeatedly in research--loss of electrolytes does not cause cramping. I've yet to find study that shows it does. Has anyone seen such a study?

At December 30, 2008 5:39 AM , Anonymous John Martinez said...


I'd agree with your premise about muscle fatigue being the primary cause of muscle cramping. Tim Noakes and Martin Schwellnus have both published quite a bit on what they term EAMC or exercise-associated muscle cramping.

Here's a link to a British Journal of Sports Medicine article by Schwellnus:

-John Martinez, MD
Coastal Sports and Wellness Medical Center
San Diego, CA

At March 12, 2009 10:56 AM , Anonymous Pl said...

Electrolytes are so important not just for overall health but for athletes who want to compete well. The electroltye balance is crucial and i just found out sugar cancels electrical potential of electrolytes, which is really important. I found this out at what do you think?


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