Exercise-Associated Muscle Cramping (EAMC)

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Do you get cramps after exercising? This article discusses 'exercise-associated muscle cramping' including the diagnosis, risk factors and some treatments.

By Jeffrey B. Kreher, MD, FAAP
Pediatric Sports Medicine

Member AMSSM

Similar to other conditions in sports medicine/exercise physiology, cramping is a relatively common affliction, affecting 30-50% of marathon runners. It is somewhat surprising that something so common can remain a topic of debate with significant variations in management.

Defined:

• EAMC is a subset of cramping defined as a “painful spasmodic involuntary contraction of skeletal muscle that occurs during or immediately after muscular exercise.”

• It does not include smooth muscle cramping or skeletal muscle cramping at rest.

Etiology:

• The most validated explanation points to faulty neuromuscular control at the spinal cord level.

• Other associations that do not prove cause and effect include electrolyte abnormalities (low potassium, low chloride, high potassium, low magnesium and low calcium, high salt concentrations in sweat, dehydration, and high temperature. Two studies in marathon runners and two studies in Ironman triathletes showed no association in electrolytes and development of EAMC. It appears that fatiguing exercise results in the abnormal neuromuscular control in the spinal cord.

• Finally, cramping can be induced by contracting an already shortened muscle.

Clinical Picture:

• Athletes with EAMC tend to have localized cramps whereas those more generalized whole-body cramps may be more likely to be associated with electrolyte/hydration issues.

• There can be more severe causes of cramps, but they tend to be much rarer. If an athlete has significant EAMC with cola-colored or very dark urine or no urine for 24 hours, he/she should be evaluated by a healthcare professional. Additional reasons to be evaluated include the following: concurrent confusion, coma or other sign related to brain malfunction, and recurrent EAMC.

Risk Factors:

• It appears EAMC is most likely to occur in conditions that lead to premature muscle fatigue in an athlete with a history of EAMC.

• In a study of marathon runners, the following factors or conditions were associated with EAMC: older age, longer history of running, higher body mass index, shorter daily stretching time, irregular stretching habits, a positive family history of cramping, high-intensity running, long duration (>30km), subjective muscle fatigue, and hill running.

• Past history of EAMC and competing at a higher than usual intensity were identified as risk factors in a study of Ironman triathletes.

Treatment:

• Passive stretching of the shortened muscle is the most effective treatment.

• In some athletes, if rest, massage, stretching and fluids do not help, consideration of 2-3L of normal saline into the vein can be considered.

Prevention:

• A majority of EAMC can be prevented by conditioning and stretching.

• In addition, an athlete should maintain adequate nutrition to prevent premature muscle fatigue and reduce the intensity and duration of training if necessary.

• Increasing salt intake may help some athletes that suffer from EAMC. This can be achieved by salting your food and consuming tomato juice, pretzels, and beef jerky.

REFERENCES
Eichner ER. “The Role of Sodium in ‘Heat Cramping.’” Sports Med. 37(4-5):368-370, 2007.
Schwellnus MP. “Skeletal Muscle Cramps During Exercise.” Phys & Sporstmed. 27(12):
Schwellnus MP. “Muscle Cramping in the Marathon.” Sports Med. 37(4-5):364-367, 2007

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date: November 4, 2007