Marathon Emergencies: From Muscle Cramps to Cardiac Arrest

Thomas Kron, MD

March 11, 2022

In 2019, there were 238 marathon competitions in Germany. More than 90% of the over 110,000 runners who started these races reached the finish, according to emergency and intensive care medics. Since running is a popular sport for many people of various age groups, risk groups, and degrees of professionalism, emergency services are confronted with a wide spectrum of medical emergencies, according to Simon-Richard Finke, MD, intensivist at University Hospital Cologne, Germany, and Daniel C. Schroeder, MD, intensivist at German Armed Forces Hospital in Koblenz, Germany. In a recent journal article, Finke, Schroeder, and colleagues explained which medical emergencies should be anticipated and how they are approached.

Exercise-Associated Muscle Cramps

The authors write that muscular overload, electrolyte imbalances, and insufficient fluid intake are discussed as the cause of painful, involuntary skeletal muscle contractions. Older and untrained athletes, as well as runners with joint displacement, are particularly affected.

Therapy: Muscle stretching and oral rehydration.


Tendinopathy is usually caused by repetitive activity, the consequence of which is progressive degeneration of the collagen fibers. Clinical symptoms include pain and loss of function. Sites affected are the Achilles tendon and plantar fascia.

Preclinical Therapy: Resting the affected limb, therefore withdrawing from the competition, and analgesia.


Possible causes of rhabdomyolysis (the rapid breakdown of damaged skeletal muscle) are traumas, medications, poisons, and pronounced thermal stress. Nonspecific initial symptoms include pain, weakness, and movement limitations. They indicate damage to the skeletal musculature, the extent of which must not be underestimated, warn the authors.

Preclinical Therapy: Analgesia and cooling. In the event of an unclear diagnosis, referral to the hospital.


Microfractures and stress fractures can arise as a result of exertion. The tibia, fibula, metatarsals, and the iliac crest are affected most of all.

Symptoms: Preexisting, increasing pain on exertion, which can be localized through palpation and is accompanied by nonspecific symptoms such as redness and swelling.

Preclinical Therapy: Rest, splinting, and analgesia.

Compartment Syndrome

Most commonly affected in runners are the anterior muscles of the shin. The symptoms are initially nonspecific (such as cramps or muscle weakness), explain the emergency medics. Later on, a clinical hardening of the muscle when in motion becomes apparent, with concomitant pain at rest, hypesthesia, and insufficient circulation.

Preclinical Therapy: Rest and analgesia. Therapy for advanced compartment syndrome includes prompt surgical intervention.

Sudden Cardiac Death/Cardiac Arrest

According to information from the authors, the incidence of cardiac arrest at running events is between 1 in 15,000 and 1 in 150,000. Men are particularly affected (93%) with an average age of 45-50 years. The affected patients often have coronary heart disease. For younger athletes, the main cause is hypertrophic cardiomyopathy. Hyponatremia and heat stroke are rare causes of cardiac arrest.


Collapse (orthostatic dysregulation) is the most common complication in long-distance runners, the emergency medics continued. The majority of patients do not require any medical care. If care is necessary, this is considered a "serious collapse" (tachycardia, hyperthermia, metabolic acidosis, and hypernatremia).

Preclinical Measures: Safeguarding the vital functions in line with the ABCDE approach (airway, breathing, circulation, disability, and exposure) as the main focus. 

Exercise-Induced Hyponatremia

Hyponatremia is defined as a serum sodium level of <135 mmol/L (135 mEq/L). It occurs in 13% of all long-distance runners, according to the authors. Exercise-induced hyponatremia is mostly asymptomatic and spontaneously reversible.

Causes: Increased oral consumption of hypotonic fluid (or hypervolemic hyponatremia) and hyperthermia (hypovolemic hyponatremia).

It is considered severe (exercise-induced) hyponatremia if the serum sodium level is <125 mmol/L (125 mEq/L). At this point, there is a danger of acute cerebral edema. Nonspecific symptoms include nausea, vomiting, ataxia and orientation problems, loss of consciousness, generalized seizures, and pulmonary edema with shortness of breath.

The clinical diagnosis of exercise-induced hyponatremia is extremely difficult, the authors write, because it can be confused easily with heat stroke or dehydration. An exact preclinical differentiation of the degree of severity is impossible. Clinical examination as per the ABCDE approach and careful surveying of the neurologic status are therefore of great importance for the preclinical estimation. In terms of the differential diagnosis, hypoglycemia must be excluded preclinically.

For patients with mild symptoms, hydration should be performed orally. Critically ill patients with severe dehydration (loss of >7% of the body weight, hypotension) or with limited oral intake (nausea, vomiting) should be hydrated intravenously. This treatment must be performed under close clinical monitoring.

Dehydration mostly affects fast marathon runners who do not drink enough fluid during the competition, whereas with slower runners, "overdrinking" is more commonly observed, according to the authors. Fast runners are in greater danger of dehydration, whereas slow runners are in greater danger of hyponatremia.

Heat Stroke

The emergency medics explain that heat stroke is characterized by a core body temperature of >104° F (>40° C), seizures, impaired consciousness, and multiple organ failure. Irrespective of the kind of sport, exercise-related heat stroke is the second most common cause of death in young athletes, with a mortality of 21%–63%.

Preclinical Therapy: Undressing and cooling (ice, towels), safeguarding the vital functions. At higher body temperatures and life-threatening clinical symptoms, immediate referral to a hospital.

Gastrointestinal Symptoms

Between 30% and 90% of endurance runners report developing gastrointestinal symptoms, continue the authors. The severity of the symptoms correlates with the distance or the extent of physical exertion. The special high-protein, high-carbohydrate and high-fat diet used by many runners encourages gastrointestinal symptoms. Mildly symptomatic patients have diarrhea, an urge to defecate, vomiting, flatulence, gastroesophageal reflux, nausea, cramps, and colic. It is possible to transition to severe symptoms such as abdominal angina, bloody diarrhea, small intestinal infarction, hemorrhagic gastritis, ischemic colitis, and rectal (occult) bleeding.

Preclinical Therapy: Symptomatic and cautious rehydration.

For more news, follow Medscape on Facebook, Twitter, Instagram, YouTube, and LinkedIn


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.