What features can help to distinguish exercise-associated muscle soreness and rhabdomyolysis associated with metabolic myopathies from exercise-associated muscle soreness seen in healthy individuals?
• Exercise history: Metabolic myopathies are associated with life-long exercise intolerance.
• Type of exercise preceding onset of symptoms: In healthy individuals, muscle soreness typically occurs after unaccustomed, eccentric exercise, which is defined as exercise involving lengthening of contracting muscles (e.g., walking down stairs).
• Timing to symptom onset: Pain occurs immediately during exercise in patients with metabolic myopathies and can be associated with myoglobinuria with the next urination after exercise. In contrast, pain usually develops after 8 to 36 hours following exercise in healthy individuals.
