Exercise-Induced Diarrhea

Ovid: 5-Minute Sports Medicine Consult, The

Exercise-Induced Diarrhea
Kimberly Harmon
  • Increased stool frequency or volume often accompanied by lower abdominal cramping, or urge to defecate associated with strenuous physical activity:
    • Normal physical examination
    • Normal laboratory and diagnostic studies
  • Synonym(s): Runner's diarrhea; Runner's trots
  • Primarily associated with running sports, but also common in cycling and reported in swimming, wrestling (1,2,3)
  • Difficulty with existing research:
    • Difficult to control all variables (diet, exercise intensity, underlying pathology such as irritable bowel syndrome)
    • Studies often lack a denominator, making a true incidence of symptoms difficult to determine.
    • Many studies are surveys with low response rates, which introduces a selection bias.
    • Subject's dietary recall often is inaccurate.
  • Prevalence of diarrhea reported from 8–60% in athletes
  • Prevalence of diarrhea in control subjects reported up to 40%
Risk Factors
  • Underlying bowel pathology may worsen with strenuous exercise.
  • Dehydration
  • Occurs more frequently with increased exercise intensity
  • Occurs more frequently in untrained participants
  • Type of exercise (running > cycling, swimming, speed skating, cross-country skiing)
  • Meals rich in fat, protein, and fiber taken shortly before exercise worsen symptoms.
Proposed mechanisms (1,2,3):
  • Mesenteric ischemia:
    • With strenuous exercise, blood is shifted away from the gut and to the working muscle.
    • Exercising at 70% VO2 max decreases blood flow to GI tract by 60–70%.
    • May lead to the production of endotoxin
    • Causes a cascade of inflammatory events that can further impair the mucosal integrity
    • Increased activity of the sympathetic nervous system leads to decreased sphlanic blood flow and is caused by:
      • Mental stress
      • Hyperthermia
      • Dehydration
      • Hypoglycemia
  • Increased sympathetic nervous system activity:
    • Suppresses parasympathetic activity
    • Decreased gut tone and resistance
    • Increased colonic transit times
    • Secretion of gastroenteropancreatic hormones
  • Mechanical stimulation of the colon due to intra-abdominal jostling
  • Enteric fluid and electrolyte balance
  • Increased stool frequency or volume, or loose stools after exercise
  • Often accompanied by abdominal cramping and urge to defecate
  • May occur just with competition and not with training
  • Normal bowel function at other times
Physical Exam
  • Increased stool frequency
  • Increased stool volume
  • Loose or explosive stools
  • Urge to defecate, often necessitating the athlete to cease exercise
  • Abdominal cramping
  • Rectal bleeding
  • Unremarkable physical examination
Diagnostic Tests & Interpretation
  • Exercise-associated diarrhea is a diagnosis of exclusion.
  • Workup is used to rule out other causes of diarrhea.
  • Stool cultures, including Clostridium difficile
  • Consider antigliadin and tissue transaminase antibodies to rule out celiac sprue.
  • Thyroid-stimulating hormone
  • Consider stool osmolar gap if eating disorder and/or laxative abuse is suspected:
    • Increased osmotic gap is suspicious for laxative use.
Imaging studies should be obtained as clinically indicated:
  • Consider barium enema
  • Contrast-enhanced CT scan
Diagnostic Procedures/Surgery
Diagnostic procedures such as sigmoidoscopy or colonoscopy may be considered as clinically indicated.


Differential Diagnosis
  • Irritable bowel disease
  • Inflammatory bowel disease
  • Infection
  • Colon cancer
  • Superior mesenteric or portal venous thrombosis
  • Malabsorption
  • Microscopic colitis
  • Laxative abuse
  • Lactose intolerance
  • Hyperthyroidism
Ongoing Care
Dietary modification can be helpful (1,2,3)[C]:
  • Stay well hydrated.
  • Avoid caffeine, which is both a diuretic and a cathartic.
  • Avoid foods that exacerbate symptoms (eg, lactose in lactose-intolerant athlete).
  • Limit intake of gas-forming foods (broccoli, onions, beans).
  • Eat a small, low-fat, low-fiber meal several hours before competition:
    • Use low-osmolar sports drink between meal and competition or training.
  • Avoid large doses of vitamin C, sodium bicarbonate, and carbohydrate drink prior to exercise.
  • If athlete still has difficulty with diarrhea or urge to defecate, try complete nutritional liquid that is low in fiber during the day preceding competition.
Most athletes can learn how to manage their symptoms through the use of diet and training.
1. Casey E, Mistry DJ, MacKnight JM. Training room management of medical conditions: sports gastroenterology. Clin Sports Med. 2005;24:525–540, viii.
2. Ho GW. Lower gastrointestinal distress in endurance athletes. Curr Sports Med Rep. 2009;8:85–91.
3. Simons SM, Kennedy RG. Gastrointestinal problems in runners. Curr Sports Med Rep. 2004;3:112–116.
Additional Reading
Green GA. Gastrointestinal disorders in the athlete. Clin Sports Med. 1992;11:453–470.
Swain RA. Exercise-induced diarrhea: when to wonder. Med Sci Sports Exerc. 1994;26:523–526.
  • 306.4 Gastrointestinal malfunction arising from mental factors
  • 564.5 Functional diarrhea
  • 787.91 Diarrhea

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