Muscle Cramping in the Endurance Athlete

author : AMSSM

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Learn about the symptoms, theory and treatment of Exercise Associated Muscle Cramping (EAMC).

By Jeff Rosenberg MD
Member AMSSM

Symptoms
Exercise associated muscle cramping (EAMC) is a phenomenon of painful involuntary muscle contractions. This problem has been reported to affect 30% to 50% of endurance athletes participating in marathons and triathlons. The etiology has not been full elucidated and experts feel there may possibly be several distinct types of cramps. When attempting to determine the cause of EAMC in an individual, it is important to rule out medical problems that can masquerade as EAMC including muscle pain from the use of cholesterol lowering ‘statin’ medications, peripheral vascular disease, nighttime cramping, dehydration, and pain from a sickle cell crisis.

Electrolyte imbalance
The most cited theory explaining muscle cramping is an electrolyte imbalance in the blood, most likely sodium loss through sweating. The origin of this theory evolved over 100 years ago with studies on individuals working in high temperature, high humidity environments such as during the creation of the Hoover Dam. These cramps were associated with profuse sweating and electrolyte changes. Improvement occurred with intravenous salt water and oral salt water replacement. This kind of cramping was initially called ‘heat cramps”. It is now recognized that this is a misnomer because EAMC can occur in cool weather as well.

Not all of the literature supports the theory of dehydration and sodium imbalance causing cramping: one study evaluating Ironman distance triathlon finishers found that those who developed EAMC where not statistically more dehydrated and did not have greater electrolyte abnormalities when compared with non-cramping finishers.

Or ill communication?
An opposing theory attributes EAMC to the loss of communication signals between muscles and nerves caused by muscle fatigue. Muscle fatigue occurs as athletes exercise at high intensity and at lower intensities for long periods of time. One can develop EAMC in the following settings: poor conditioning prior to a race, higher intensity exercise (during a race and usually not while training), and near the end of an event after prolonged activity. The muscles are more ‘excitable’ and start to electrically twitch. As fatigue continues, this twitch can escalate into a full blown cramp in which the whole muscle completely tightens. Stretching the muscle increases the ‘relaxation’ signal to the muscle and aids in relieving the painful cramp.

Prevention
It is not completely clear why individuals who have had EAMC in the past are more likely to experience it again. Prevention should not solely concentrate on adequate hydration and electrolyte levels. Endurance athletes should try to prevent muscle fatigue in the large muscle groups used for their events such as the quadriceps, hamstrings, and calf muscles. A long term gradual strengthening program which consists of recruiting muscles at high intensity during training can delay the potential localized muscle fatigue required to start muscle twitching and EAMC while racing. In addition, biomechanical evaluation to determine if certain muscles are being inappropriately overused and thereby predisposing to fatigue can be helpful.

Treatment
Once EAMC begins, the immediate treatment is stretching of the affected muscle groups. Muscle cooling with application of ice to the affected area or drinking more electrolytes is no more successful in releasing the muscle cramp than vigorous stretching of the muscle group.

Jeff Rosenberg MD
Director Mountainside Sports Medicine Fellowship
Assistant Residency Director Mountainside Family Medicine Residency
Verona, NJ

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date: August 7, 2009