What causes exercise-induced headaches?

Causes of Exercise-Induced Headache

Exercise-induced headaches result from multiple mechanisms including dehydration and electrolyte disturbances, elevated core body temperature, vascular changes during exertion, and in some cases represent primary exercise headache (a benign idiopathic condition) or exercise-triggered migraine. 1, 2

Primary Mechanisms

Heat and Dehydration

• Dehydration and electrolyte alterations, particularly in hot environments, are major contributors to exercise-induced headache. 1
• Heat-related headaches occur when core body temperature rises excessively, coupled with inadequate fluid replacement during physical activity. 1
• Headache is a cardinal symptom of heat exhaustion and can progress to heat stroke if core temperature exceeds 104°F (40°C). 3
• The American Heart Association identifies headache as a key warning sign of heat stress during exercise, along with dizziness, faintness, nausea, and cramps. 3

Vascular and Metabolic Factors

• Exercise can trigger migraine attacks through acute release of neuropeptides such as calcitonin gene-related peptide (CGRP) or alterations in hypocretin or lactate metabolism. 4
• Approximately 10% of exercise headaches have an organic (secondary) origin that requires investigation. 2
• The condition affects 1-26% of the adult population, with most cases being benign primary exercise headache. 5

Dilutional Hyponatremia

• Exercise-associated hyponatremia (EAH) presents with headache as an initial symptom, caused by excessive fluid consumption relative to sodium stores during prolonged exercise. 3, 6
• This dilutional hyponatremia can progress to severe symptoms including altered mental status, seizures, and cerebral edema if untreated. 3, 6

Clinical Evaluation Red Flags

You must investigate these characteristics to distinguish benign from dangerous causes: 1, 5

• Neurological symptoms (focal deficits, altered consciousness, visual changes) require immediate medical evaluation. 1
• Atypical presentation features: recent onset in older individuals, prolonged duration beyond typical patterns, or progressive worsening. 1, 5
• Associated systemic symptoms: nausea, vomiting, fever, or signs of heat illness. 1
• Temporal relationship: onset during versus after exercise, and specific triggering activities. 1

Contributing Factors to Assess

• Environmental conditions: High temperature (>70°F) and humidity increase risk substantially. 3
• Hydration status: Both dehydration and overhydration (leading to hyponatremia) can cause headache. 3
• Timing of meals: Exercising within 2 hours of eating increases risk due to competing blood flow demands. 3
• Medication use: NSAIDs or aspirin taken before exercise may contribute in some individuals. 7
• Personal history: Atopy, family history of migraine, or previous episodes. 7, 2

Pathophysiological Context

Primary exercise headache is a diagnosis of exclusion after ruling out secondary causes. 2, 5

• The mechanism involves altered pain modulation through endogenous opioids, endocannabinoids, and neuropeptides (CGRP, BDNF). 8, 4
• Regular exercise may actually increase the migraine threshold through elevated beta-endorphin and endocannabinoid levels, explaining why chronic exercisers have fewer attacks despite acute triggering potential. 4
• Exercise-induced migraine differs from benign exertional headache but can be difficult to distinguish clinically without careful history. 2

Important Clinical Pitfalls

• Do not assume all exercise headaches are benign - neuroimaging is indicated for atypical presentations, new onset in older patients, or any neurological symptoms. 1
• Distinguish from related conditions: Cholinergic urticaria presents with punctate wheals and increased core temperature without vascular collapse, while exercise-induced anaphylaxis includes systemic symptoms beyond isolated headache. 7
• Consider food-dependent exercise-induced anaphylaxis (FDEIA) if headache occurs only when exercise follows specific food ingestion within 4-6 hours. 7
• Recognize hyponatremia early - it presents with headache, nausea, and bloating before progressing to altered mental status, and affects 3-22% of marathon runners. 3, 6