A Long-Running Mystery, the Common Cramp

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A Long-Running Mystery, the Common Cramp

http://www.nytimes.com/2008/02/14/health/nutrition/14BEST.html?

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By Kolata

It can happen for no reason, it seems, taking you completely by

surprise. And it can be excruciating. Suddenly, a muscle contracts

violently, as if it had been prodded with a jolt of electricity. And

it remains balled in a tight knot as painful second after painful

second drags on.

A seized calf muscle or a hamstring can be frightening. Swimmers fear

they will drown. Cyclists nearly fall off their bikes. Runners drop

to the ground, grimacing, gritting their teeth.

The contraction is so strong that you could not will yourself to ball

your muscle that tightly. And your muscle is likely to feel sore the

next day.

You have had a cramp, an experience so common among endurance

athletes, researchers say, that almost everyone who has tried

endurance sports has had a muscle cramp or has a friend who has had

one.

Cramps afflict 39 percent of marathon runners, 79 percent of

triathletes, and 60 percent of cyclists at one time or another, said

Dr. P. Schwellnus, a professor of sports medicine at the

University of Cape Town.

Cramps can occur during exercise, immediately after, or he said, as

long as six hours later.

Yet common as they are and terrible as they can be, no one really

understands cramps. They are a medical mystery.

" I would say, bottom line, there is no really convincing biological

explanation for muscle cramps, " said Dr. Marks, a muscle

researcher and chairman of the department of physiology and cellular

biophysics at Columbia University College of Physicians and Surgeons.

Medical textbooks skirt the topic, he added, often avoiding any

explanation. And few scientists have studied cramps.

But as anyone who has ever complained of cramps will attest, lots of

advice is circulating on how to avoid them and lots of people —

friends, coaches, doctors — think they have a solution.

Take a multivitamin pill to get zinc and magnesium. Massage the

muscles. Drink plenty of water. Be sure to get enough electrolytes

like sodium and potassium. Stretch before you start to exercise. No,

stretch as soon as you finish. See a nutritionist to correct

imbalances in your diet. See a trainer to be sure you are moving

correctly.

Of course, Dr. Marks said, medical conditions can lead to cramps,

including narrowed blood vessels, usually from atherosclerosis, or

compression of a nerve, as happens in spinal stenosis. Cramps also

can arise from hypothyroidism. And they can be a side effect of

medications like diuretics, used to lower blood pressure, which can

lead to a potassium deficiency that can cause cramps.

But, he and others said, those conditions do not explain the vast

majority of cramps.

" You are left with the fact that cramping usually occurs in healthy

people without any underlying disease, " Dr. Marks said.

There are three leading hypotheses about how to treat cramps and how

to prevent them.

There's the dehydration proposal: you just need more fluid. But, Dr.

Schwellnus said, he studied athletes who cramped and found that they

were no more dehydrated before or after a race than those who did not

have cramps.

Then there's the electrolyte hypothesis: what you really need is

sodium and potassium.

F. Bergeron, who directs the environmental physiology

laboratory at the Medical College of Georgia, said the electrolyte

hypothesis applies to a specific type of cramp that is related to

excessive sweating. It occurs, he said, when the fluid that bathes

the connection between muscle and nerve is depleted of sodium and

potassium, which was lost through sweat. The nerve then becomes

hypersensitive, Dr. Bergeron said.

" Usually you feel little twitches first, " he explained. " They last

for 20 to 30 minutes and if you don't do anything you can be in full-

blown cramps. " Those cramps, he continued can move from place to

place on your body, from one leg to the next, to your arms, stomach,

even your fingers or your face.

The solution, Dr. Bergeron said, is to drink salty fluids like

Gatorade (the company sponsors his research). He said he had

prevented cramps in tennis players this way.

But asked whether there are any rigorous studies to confirm this

hypothesis, he said no. " We haven't done the study yet, " he

said. " We're at the point of kind of connecting the dots. "

The third hypothesis is advanced by Dr. Schwellnus. He questions the

electrolyte hypothesis because his studies of Ironman-distance

triathletes as well as other studies of endurance athletes found no

difference in electrolyte levels between those who suffered cramps

and those who did not.

DR. SCHWELLNUS proposes that the real cause of cramping is an

imbalance between nerve signals that excite a muscle and those that

inhibit its contractions. And that imbalance, he said, occurs when a

muscle is growing fatigued.

His solutions for cramps are to exercise less intensely and for

shorter times, to be sure you had enough carbohydrates to fuel your

muscles, to train sufficiently and to regularly stretch the muscles

that give you problems. These recommendations are based on his recent

study of Ironman triathletes, Dr. Schwellnus said.

But while he advocates those practices, he said, they have not been

proved in a rigorous study.

In the meantime, some doctors have resorted to experimenting on

themselves, devising their own explanations and cures.

Dr. van der Horst, an AIDS researcher at the University of

North Carolina, said he was stunned when his calf started to cramp

without warning when he was running. The pain was almost unbearable,

he said, and even when the muscle finally relaxed, it cramped again

when he resumed running.

" I started carrying a cellphone with me on long runs, " Dr. van der

Horst said. When a cramp struck, he called his wife to ask her to

drive out and get him.

" I think I was getting calcium deposits or something, " Dr. van der

Horst said.

His solution was to massage his calves at all hours, pushing deep

into the muscle. This seems to work, he said, explaining that it's

been a year now since he had a cramp.

Dr. Liggett, a professor of medicine and physiology at the

University of land, has a different solution. He got terrible

cramps in his calf during yoga. The culprit, he decided, was the

drugs he takes for asthma, which can diminish the body's supply of

potassium. He knew that potassium is sold over the counter. But

because high levels of potassium can be dangerous, store-bought

potassium supplements are not very strong.

Dr. Liggett's solution is not one anyone who is not a doctor should

try at home. Before he does yoga, he measures the potassium levels in

his blood before and after taking what he describes as a hefty dose

of over-the-counter supplement. Then he calculates how much

additional potassium he thinks he needs, securing it from

concentrated potassium tablets from his research lab — how much he

declined to say.

" I didn't want to drink two gallons of Gatorade, " Dr. Liggett

explained. He hasn't had cramps since he began " preloading, " as he

calls it, with potassium. But, he said, " I haven't done a controlled

trial. "

Dr. Marks, for one, is not convinced by the evidence for any of the

hypotheses, nor by any of the proposed remedies.

What causes cramps?

" I would say the answer to that question is still open to

investigation, " he said. And, he added, he hopes someone takes it up.