What triggers heartburn during physical activity?

Causes of Heartburn During Workout

The primary causes of heartburn during physical activity include decreased blood flow to the digestive tract (splanchnic hypoperfusion), mechanical factors such as body position and impact, and nutritional choices before and during exercise. 1

Physiological Mechanisms

Reduced Blood Flow

• During exercise, blood is redirected from the digestive system to working muscles
• This splanchnic hypoperfusion can lead to:
  • Reduced esophageal sphincter tone
  • Decreased gastric emptying
  • Compromised gut barrier function 1

Mechanical Factors

• High-impact activities (running) cause more symptoms than low-impact activities (cycling, swimming)
• Exercise posture affects symptom prevalence:
  • Forward-leaning positions (cycling "aero" position) increase upper gastrointestinal pressure
  • Repetitive jarring movements during running can trigger lower gastrointestinal symptoms 1
• Increased respiratory rate during exercise can lead to "swallowing" air, contributing to stomach distress 1

Nutritional Triggers

• Consuming certain foods/beverages before or during exercise:
  • High-fiber foods
  • High-fat foods
  • Acidic foods (citrus, carbonated drinks)
  • Spicy foods
  • Coffee and alcohol
  • Concentrated carbohydrate solutions with high osmolality 1
• Dehydration can exacerbate symptoms 1

Medication Factors

• Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can:
  • Increase gastrointestinal permeability
  • Lead to mucosal bleeding or perforation
  • Aggravate exercise-induced small intestinal injury 1

Exercise Intensity Relationship

• Symptoms are intensity-dependent - higher intensity exercise causes more pronounced effects:
  • Mild-to-moderate exercise is generally protective for gut health
  • Strenuous exercise significantly increases risk of heartburn and other GI symptoms 2
• Elite athletes report higher prevalence of symptoms (1.5-3.0 times) compared to recreational exercisers 2

Prevention Strategies

Nutritional Adjustments

• Avoid high-fiber foods in the days before intense exercise
• Avoid NSAIDs (especially ibuprofen) before exercise
• Avoid exclusively fructose-containing drinks (glucose-fructose combinations may be better tolerated)
• Stay well-hydrated before and during exercise
• Use carbohydrate drinks with appropriate concentration and osmolality 1
• For those with nighttime symptoms, avoid eating 2-3 hours before bedtime 1

Exercise Modifications

• "Train the gut" - gradually accustom your digestive system to fluid and food intake during exercise
• Athletes unaccustomed to eating/drinking during exercise have twice the risk of symptoms 1
• Consider lower-impact activities if symptoms persist (swimming, cycling instead of running) 1
• Include proper warm-up and cool-down periods 1

Body Position Considerations

• For those with symptoms when recumbent, elevate the head of the bed 1
• Be mindful of exercise positions that increase abdominal pressure

Weight Management

• Weight loss should be advised for overweight or obese individuals with GERD symptoms 1

When to Seek Medical Attention

• If experiencing chest discomfort during exercise that could be confused with cardiac symptoms
• If symptoms persist despite preventive measures
• If experiencing severe symptoms like bloody diarrhea or severe abdominal pain 1

Remember that while some degree of gastrointestinal discomfort during intense exercise is common (affecting 30-90% of endurance athletes), persistent or severe symptoms warrant medical evaluation to rule out more serious conditions 1.