Post-exertional discomfort

Specialty: General.

• post-exercise collapse
• delayed fatigue after effort
• post-exertion symptomatic worsening

Why it occurs

• Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (in which the immune system and the autonomic nervous system react abnormally to mild physical, mental or emotional activity, causing systemic collapse)
• Dysautonomia or postural orthostatic tachycardia syndrome (SSTPO/POTS, where the ineffective cardiovascular response to exertion causes cerebral hypoperfusion and delayed systemic fatigue)
• Primary or secondary mitochondrial dysfunction (alterations in the electron transport chain that prevent the rapid recovery of muscle phosphagen stores)
• Metabolic myopathies (McArdle disease or carnitine palmitoyltransferase deficiencies, which block energy production during exercise)
• Post-viral fatigue syndrome (state of immune deregulation after serious infections that lasts for months).

Initial workup

Cardiopulmonary stress test with measurement of expired gases (ideally a protocol of two consecutive days to evaluate the fall of the anaerobic threshold), 24-hour electrocardiographic Holter, stress echocardiogram, and muscle metabolic panel that includes pre- and post-exertion serum lactate and pyruvate.

Standard management

• Fludrocortisone — 0.1 mg orally daily in confirmed cases of dysautonomia with orthostatic hypotension, to increase plasma volume
• Coenzyme Q10 combined with NADH — 100 mg and 10 mg respectively per day to support mitochondrial function and ATP synthesis
• Propranolol (10 to 20 mg orally two or three times a day in low doses, useful to mitigate the exaggerated sympathetic response in POTS).