Clinically speaking, a muscle cramp is “a painful, spasmodic, involuntary, contraction of skeletal muscle,” but for the runner writhing on the ground it’s an ever-tightening knot that hurts like hell.

A cramp may sound insignificant to those who have never experienced one, but they arouse great fear and anxiety among athletes, looming like a dark cloud over all endurance events, especially marathons, which record a high rate of incidence.

It might surprise you to learn what doesn’t cause your exercise-associated muscle cramps (EAMC).

“Among the findings in the last two years are that dehydration is not linked to the development of cramping, that crampers do not have disturbances of the blood electrolyte concentrations—mainly sodium, chloride, magnesium. There is evidence now that the muscles of crampers have increased electromyographic activity (are more ‘twitchy’) at the end of the race. The latter fits in with the idea that as muscle fatigues, it appears that in some individuals (genetic predisposition) it upsets the normal control of nerve signal input to the muscle, and the muscle is more excitable or twitchy. If exercise continues, then a threshold is exceeded and the contraction is sustained—and they develop a cramp,” says Dr. Martin P. Schwellnus, professor of sports medicine at the University of Cape Town in South Africa and a leading authority on the subject of exercise-associated muscle cramps.

Historically, muscle cramping was attributed to dehydration and electrolyte deficiency, probably as a result of superficial observation of laborers on steamships made a century ago, which Dr.Schwellnus makes note of in an article published in the Physician and Sportsmedicine (www.physsportsmed.com).

A theory evolved, which remains prevalent to this day, suggesting that perspiration depletes the body of fluids and electrolytes, inducing fatigue, subsequently leading to cramps.

Research conducted by Dr. Schwellnus, however, has resulted in a far more sophisticated explanation.

“It appears that as muscle fatigues, there is greater excitatory nerve activity and less inhibitory nerve activity to the muscle. A cramp appears to represent this imbalance in an exaggerated form, i.e. excitatory input is high and inhibitory input very low, and this results in increased ‘twitchiness.’ We have labeled this the ‘cramp prone state.’ Athletes that exercise and start to develop this, complain of fatigue, muscle fasciculations (visible muscle contractions despite resting). If exercise continues, a cramp will develop.”

Dr. Schwellnus’s research suggests there may be an underlying genetic or hereditary component to muscle cramps.

“We have shown in a number of studies that crampers have a higher prevalence of a positive family history,” he comments. “Although indirect evidence, this does suggest a genetic predisposition.”

An epidemiologic study of 1,300 marathon runners conducted by Dr. Schwellnus, identified a number of risk factors for exercise-associated muscle cramps, among them older age, an extended history of running, large body mass index, inadequate and inconsistent stretching regimes, and a family history of the problem. High-intensity exercise, as well as prolonged exercise sessions, and hill running also emerged as factors.

“The two most important observations from these data,” he writes in the Physician and Sportsmedicine, “are, first, that EAMC is associated with running conditions that can lead to premature muscle fatigue, and, second, that poor stretching habits appear to increase the risk for EAMC. Poor stretching habits could lead to an exaggerated myotonic reflex, thereby increasing spindle activity.”

Since runners subject themselves to more stress than most athletes, it’s not surprising they record the highest rate of cramping. A chronic sufferer of this malady might be tempted to switch sports, but Dr. Schwellnus advises otherwise: “We have studied cramping in cyclists so it definitely occurs. The advice is usually not necessarily to shift to an alternative sport, but rather to make sure that race preparation is optimal, so that premature fatigue is prevented. However, a lower-intensity-exercise sport can be recommended to those athletes with severe cramping.”

Televised sporting events often include the sight of a prone athlete disabled by a cramp, prompting analysts to comment on the need for more fluid intake: “Got to keep up those salt levels,” is a frequently heard remark on broadcasts. It’s rare to hear anyone enlarge upon the problem of exercise-associated muscle cramps, which has far more to do with inadequate preparation than low sodium. So the next time you cramp up, don’t just reach for a sports drink—conduct a thorough assessment of your training program with the aim of identifying any weaknesses.

Attack of the Cramp Monsters:

Cramps are an ever-present threat for all athletes, who must guard against muscle fatigue. Undertake these steps to minimize the occurrence of disabling cramps:

• The better conditioned you are the less likely it is that you’ll experience cramps. Improper training invites trouble, due to muscle fatigue.
• Make stretching an integral part of your training regime. Concentrate on muscles prone to cramping, such as calves.
• Eat a well-balanced diet, with special emphasis on carbohydrates.
• Moderate exercise and lessen duration if cramping persists.