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The downed runner/collapsed athlete involves anyone who cannot stand or walk unaided, either during or at the completion of an endurance athletic event.


Exercise-associated collapse may be secondary to a variety of causes, including cardiovascular compromise (postural hypotension, cardiac arrhythmia), heat-related illness (hyperthermia, hypothermia), electrolyte abnormalities (hyponatremia, hypoglycemia, rhabdomyolysis, drug toxicity), respiratory compromise (asthma, exercise associated anaphylaxis), musculoskeletal injury (cramps, fracture, tendon tear), and seizures.

Epidemiology including risk factors and primary prevention

In 2015, over 17 million athletes participated in a running event in the United States.1 Exercise-associated collapse is the most common reason for a medical encounter, most common in marathons (85-89%).2,3 Cardiac fatalities are rare, with the incidence higher in marathons (1.01 per 100,000) than half-marathons (0.27 per 100,000).4 Risk factors for collapse include medical illnesses (e.g., coronary disease), medications (including supplements), inappropriate training, warmer temperature, increased humidity, increased consumption of water (Hyponatremia), weight gain, race time > 4 hours and low body mass index (BMI).


The pathophysiology of exercise-associated collapse in the runner will depend upon the exact cause.5,6 The three most common areas are:

  1. Cardiovascular: Postural hypotension is due to the abrupt cessation of lower extremity muscle pumping actions, cutaneous vasodilatation with venous pooling of blood in the lower extremities and reduced baroreflex control, resulting in orthostatic intolerance. An acute coronary event will occur from excessive stress/fatigue in the setting of preexisting or acute coronary/cardiac abnormalities (atherosclerosis, hypertrophic cardiomyopathy, myocarditis, arrhythmia, etc).4,5
  2. Heat-related illness: Thermoregulatory compromise resulting in excessive heat gain (hyperthermia) or heat loss (hypothermia) due to hypothalamic dysregulation. Hyperthermia is secondary to excessive exercise, increased ambient temperature/humidity, inability to sweat, compromised cardiovascular reserves and/or medications. Hypothermia is secondary to cold ambient temperature in the setting of fatigue or glycogen depletion.6,7
  3. Electrolyte abnormalities: Hyponatremia is multifactorial in nature and is due to increased water ingestion and/or defects in the hormonal/renal control mechanisms. Studies suggest a linear relationship between water consumption, weight gain and hyponatremia.5,6,8-10 Inappropriate stimulation of vasopressin due to excessive exercise, fatigue and emotional stress may cause increased secretion of sodium or decreased excretion of water. Hypoglycemia is due to depletion of glycogen stores with inadequate intake of nutrition

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

Cardiovascular illness: Postural hypotension is the most common etiology for collapse, typically occurring after crossing the finish line. The athlete cannot stand and may briefly lose consciousness. Most athletes recover with minimal treatment. Sudden loss of consciousness before the end of the race suggests a more serious cardiac event (coronary event, arrhythmia).

Heat-related illness: Hyperthermia varies from heat exhaustion (headache, dizziness, weakness, euthermic or mild hyperthermia, moist skin, tachycardia, +/- altered mental status) to more severe heat stroke (weakness, temp > 40oC/104oF, dry skin, tachycardia, seizures, severely altered mental status or coma). Hypothermia may be mild (shivering, tachycardia, tachypnea, temp 32-35oC), moderate (loss of shivering, bradypnea, bradycardia, arrhythmia, CNS depression, temp 28-32oC) or severe (pulmonary edema, bradycardia, coma temp < 28o C).

Electrolyte abnormalities: Hyponatremia (Na < 135 mmol/L) may be mild (dizziness, nausea, muscle cramping, no significant confusion), moderate (headache, vomiting, lethargy, agitation, confusion), or severe (seizure, loss of consciousness). Hypoglycemia may be mild (weakness, tremor, lightheadedness, diaphoresis, tachycardia, no significant mental status change), or severe (significant change in mental status including coma).

Respiratory: Respiratory compromise may include asthma (dyspnea, tachycardia, altered mental status) or exercise-associated anaphylaxis: (pruritus, urticaria, flushing, dyspnea, chest tightness, headache).

Acute musculoskeletal injury: Often mild in nature (muscle strain, tendonitis), typically involving the lower extremities. More severe injuries may represent a fracture or tendon tear.

Neurocognitive: Seizures will present with loss of consciousness and collapse with muscle twitching.

Specific secondary or associated conditions and complications

Prompt recognition and treatment of all conditions is essential to avoid significant morbidity or mortality, depending upon the cause of collapse as outlined above.



On-scene providers often must triage, assess, and take initial measures without knowing much if any of the patient’s history.5,6,11 Pertinent history should include:

  1. Location of collapse: Collapse in the middle of a race is more likely to represent a serious condition, versus collapse at the finish.
  2. Current symptoms
  3. Past medical history: Cardiac disease, diabetes, history of exercise collapse
  4. Current medications and supplements
  5. Nutritional intake: Type and amount of fluid / food ingested before and during the race
  6. Pre- and post-race weight (if known)

Physical examination

Address life-threatening issues focusing on level of responsiveness, airway patency, breathing, circulation and any obvious bleeds and other exposures (e.g., open fractures). Once stabilized, a secondary assessment should occur in the medical tent or hospital. Focus on vital signs: temperature (rectal is most accurate to detect hyperthermia), blood pressure (including orthostatics), heart rate, respiratory rate, O2 level; cardiopulmonary system: heart rate, rhythm, murmurs, respirations, wheezing, rales, rhonchi; neurocognition: alertness, orientation, immediate/delayed recall, concentration, balance, cranial nerves, speech. Finally assess musculoskeletal system: strength, sensation, reflexes, limb alignment, spine/limb stability.

Functional assessment

The emotional state of the endurance athlete could entail depression, anxiety or other psychological reason for mood impairment. An assessment should include understanding the athlete’s purpose for running (e.g., milestone, charity, qualification for future race).

Laboratory studies

Potential onsite tests includes:

  1. Blood sodium – evaluate for hyponatremia (NA < 135 mmol/L)
  2. Blood glucose – evaluate for hypoglycemia (Glu < 65-70 mg/dL)
  3. Blood bun/creatinine – assess renal function, hydration status
  4. Blood CPK – assess for rhabdomyolysis
  5. Urine sodium, osmolality, myoglobin – assess renal function, hydration status, rhabdomyolysis.


Imaging modalities (e.g., x-rays, magnetic resonance imaging [MRIs]) are not typically available on-site. Ultrasound is becoming more available to assess for injuries (e.g., musculoskeletal injuries, cardiac).

Supplemental assessment tools

An electrocardiogram (ECG) can be done to assess cardiac rhythm. This can be performed using an automated cardiac defibrillator if a full ECG is not available.

Early predictions of outcomes

Early defibrillation has the greatest impact on cardiac arrest survival. Survival rates decrease 7-10% per minute for every minute defibrillation is delayed.4


Environmental risk factors contributing to exercise-associated collapse include warmer temperatures, increased humidity and lack of acclimatization to altitudes.

Professional Issues

Communication of an athlete’s medical status must be handled in a confidential manner. Questions from the media should be handled only by the race medical director.


Available or current treatment guidelines

A variety of published papers exist that summarize the evaluation and treatment of the collapsed running athlete.5-8 Several organization have provided position statements relating to the treatment of heat-related illness7 and exercise-associated hyponatremia.8 All emphasize the importance of rapid evaluation and treatment to avoid significant morbidity and mortality.

At different disease stages

Cardiovascular illness: If the athlete is not hyperthermic, institute supportive care (dry off, keep warm/cool, lay flat with legs elevated, remove wet clothes). Hydrate with oral or intravenous fluids (only after measuring electrolytes), as appropriate. Most athletes can be discharged to home. If there is a concern for cardiac arrest, activate advanced cardiopulmonary life support, including establishing patent airway, IV access and defibrillator/cardiac monitor. Once stable, transfer to a medical facility.4,5,6 ,11

Heat-related illness: In cases of hyperthermia, milder forms can successfully be treated with rest, hydration and active cooling (Temp > 102° F), as appropriate. Cooling methods include whole body ice immersion (rate 17° F/ hr) or rotating ice packs around neck, axilla and groin (rate 15° F/ hr). Stop active cooling at 102° F. Milder forms may be discharged, while more severe cases require transfer to a medical facility. In hypothermia, milder forms undergo passive external warming (blankets) or active external rewarming (heated blankets, forced heated air). Moderate/severe cases should undergo rewarming and transfer to a medical facility.7

Electrolyte abnormalities: In cases of hyponatremia, avoid isotonic and hypotonic fluids. Milder forms will respond to fluid restriction, close observation, natural diuresis and discharge to home once stable. For moderate/severe cases, consider 100 ml of 3% NaCl over 10 minutes x 2, oxygen, and transfer to medical facility. In hypoglycemia, milder forms will respond to 15-20 g of fast-acting carbohydrate, rechecking glucose level until normal. Moderate/severe cases may require Glucagon injection, dextrose (50%) in water (D50W) and transfer to medical facility. In cases of rhabdomyolysis or drug toxicity, stabilize and transfer to a medical facility.6,8,9

Respiratory: Most cases of asthma may be treated with supplemental oxygen and bronchodilators (e.g., beta 2 agonists). Severe cases should be transferred to a medical facility. If there is concern for exercise-associated anaphylaxis, maintain airway patency, provide epinephrine, supplemental oxygen, and transfer to medical facility.

Acute musculoskeletal injury: Treatment should be to stabilize the injured area. Cramps may be treated with rest, massage, hydration and medication (e.g., Valium). Any concern for fracture, ligament injury or tendon tear should prompt transfer to medical facility.

Neurocognitive: Any athlete experiencing a seizure should be stabilized and transferred to a local medical facility.

Coordination of care

Rapid assessment and treatment of the collapsed athlete requires efficient, well-coordinated care. Team members should be instructed prior to the race regarding roles, treatment protocols, location of medical supplies, communication capabilities and medical chain of command. Athletes assessed in the field should be transferred to medical tents or medical facilities.

Patient & family education

Most large longer-distance races have “race expos” at packet pick-up prior to the event. This is the time for medical staff to provide educational lectures regarding preventive strategies for avoiding serious medical illnesses. Recreational athletes may also find an array of evidence-based and professional resources on-line.

Emerging/unique Interventions

The majority of athletes who experience exercise-associated collapse will be treated appropriately and discharged to home. The incidence of a fatal cardiac event in long-distance running events is low (1.01 per 100,000 marathoners; 0.27 per 100,000 half-marathoners).4

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

Any physician covering a running event should be prepared to assess and treat the collapsed runner in an efficient manner, remembering: Primary assessment focuses on addressing life-threatening illnesses, Secondary assessment addresses common medical illnesses, while noting:

  1. Isotonic/hypotonic fluids should be avoided in cases of hyponatremia.
  2. Hyperthermia requires rapid cooling through whole-body ice immersion.

Educate athletes prior to discharge about preventive strategies (e.g., training, nutrition, environment


Cutting edge concepts and practice

There are a growing number of racers participating in longer-distance events (e.g., ultramarathons). Limited research3,7 suggests that ultramarathon runners experience different rates of injuries and hyponatremia than marathon runners. Current research is focusing on identifying risk factors for collapse and the role of aggressive use of hypertonic solutions for hyponatremia in these athletes.



  1. Running USA. 2011 Annual Marathon Report. http://www.runningusa.org/ (accessed May 20, 2016)
  2. Roberts WO. 12-yr profile of medical injury and illness for the Twin Cities Marathon. Med Sci Sports Exerc. 2000;32(9):1549-1555.
  3. Krabak BJ, Waite B, Schiff MA. Study of injury and illness rates in multiday ultramarathon runners. Med Sci Sports Exerc. 2011;43(12):2314-2320.
  4. Kim JH, Malhotra R, Chiampas G, et al. Cardiac arrest during long-distance running races. N Engl J Med. 2012:366(2):130-140.
  5. Asplund CA, O’Connor FG, Noakes TD. Exercise-associated collapse: an evidenced-based review and primer for clinicians. Br J Sports Med. 2011;45:1157-1162.
  6. Hoffman M, Bassett P, Hill J, Khodaee, M, Krabak BJ, Lipman G, Pasternal P, Roger I, Sheer B, Townes DA. Medical services at ultra-endurance foot races in remote environments: medical issues and consensus guidelines. Sport Med. 2014 Aug:44(8): 1055-69.
  7. Casa DJ, DeMartini JK, Bergeron MF, Csillan D, Eichner ER, Lopez RM, Ferrara MS, Miller KC, O’Connor F, Sawka MN, Yeargin SW. National athletic trainers’ association position statement: Exertional heat illnesses. J Athl Train. 2015Aug 18 [Epub ahead of print].
  8. Hew-Butler T, Rosner MH, Fowkes-Godek S, Dugas JP, Hoffman MD, Lewis DP, Maughan RJ, Miller KC, Montain SJ, Rehrer NJ, Roberts WO, Rogers IR, Siegel AJ, Stuempfle KJ, Winger JM, Verbalis JG. Statement of the 3rd International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Br J Sports Med. 2015 Nov;49(22):1432-46
  9. Krabak BJ, Parker KM, DiGirolamo A: Exercise Associated Collapse: Is Hyponatremia in our Head? PMR. 2016 Mar;8(3): S61-68
  10. Noakes TD, Sharwood K, Speedy D, et al. Three independent biological mechanisms cause exercise-associated hyponatremia: evidence from 2,135 weighed competitive athletic performances. Proc Natl Acad Sci USA.2005;102(51):18550-18555. Epub 2005 Dec 12.
  11. Childress MA, O’Connor FG, Levine BD. Exertional collapse in the runner: evaluation and management in fieldside and office-based settings. Clin Sports Med. 2010;29:459-476.

Original Version of the Topic:

Brian J. Krabak, MD, MBA, Andrew H. Gordon, MD, PhD. Downed runner. Publication Date: 2012/07/25.

Author Disclosure

Brian Krabak, MD, MBA, FACSM
Nothing to Disclose