Exertional Rhabdomyolysis

Question 1

Definition of ER

Answer 1

• Skeletal muscle breakdown w/ release of myocyte contents into circulation
• From stresses that injure muscle tissue
• Risk: metabolic abnormalities & acute renal failure

Question 2

Etiology of ER

Answer 2

• Strenuous exercise or exertion 24-48h prior
• Unaccustomed exercises
• Eccentric exercise more damage to muscle than concentric

Question 3

Pathophysiology of ER

Answer 3

• Unclear
• Direct injury appears to mainly affect type 2 (white) muscle
• Primary cell injury->increased Ca2+ ->secondary injury->activation
• Impaired ATP production/utilization
• Muscle injury releases K+, uric acid, Ca phosphate, myoglobin, and muscle enzymes

Question 4

Clinical Diagnosis of ER

Answer 4

• Myalgia
• Red/brown urine due to myoglobinuria
• elevated serum muscle enzymes: creatine kinase
  
  • greater than 5x-10x normal
  • however normal is different b/t individuals

Question 5

Race & Gender Role in CK Levels

Answer 5

• Males>Females
• Blacks>other races
• Athletes>non-athletes

Question 6

What determines Risk of Morbidity

Answer 6

• Can have high CK levels w/o problems & can have problems at low CK levels
• Exercise Factors:
  
  • Experience and fitness level
  • Intensity, Duration, and type
• Non-exercise Factors:
  
  • Illness
  • Sickle Cell Trait
  • Temperature
  • Drugs and nutraceuticals
  • Myopathies: muscular dystrophy, PM/DM

Question 7

Metabolic Myopathies

Answer 7

• Defect in skeletal muscle energy metabolism
• Present as myalgia, cramping, and exercise intolerance
• Myoadenylate deaminase deficiency
• Glycogen storage disease
• Fatty oxidation defects
• Mitochondrial myopathies

Question 8

High Risk Warrior Athlete

Answer 8

-Delayed clinical recovery w/ restricted activity
-Persistant CK elevation w/ 4wks rest
-ER w/ acute renal failure
Muscle injury at low/moderate work
-History of ER, SCD, malignant hyperthermia, heat injury, cramps & muscle pain
-Drug or supplement use
-CPK peak >100,000

Question 9

Exercise Intolerance Mutation Profile

Answer 9

• Screens for genetic variants associated w/ ER
• Carnitie Palmitoyltransferase II Deficiency
  
  • CPT2 gene
• Myophosphorylase Deficiency
  
  • PYGM gene
• Myoadenylate Deaminase Deficiency
  
  • AMPD1 gene

Question 10

Other tests for ER

Answer 10

• Muscle biopsy:
  
  • Myoglobinuria test panel
  • Caffeine halothane contracture test
• Heat tolerance testing
• Nerve conduction
• Two Step exercise: 5min@54 steps/min and knee ends
  
  • wearing backpack w/ 30% body weight
  • Blood sample before & after
  • High responder if CK>230

Question 11

Types of Exercise Associated w/ ER

Answer 11

• Eccentric exercise predominance
• Unaccustomed Exercise
• Sudden increase in volume or intensity
• Timed!

Question 12

Role of Sickle Cell Trait in ER

Answer 12

• 1/14 have it and protects against malaria
• Suggests greater ability of SCT carriers to perform in short intense running events
• Associated w/ hematuria, ER, & exercise related sudden death

Question 13

Role of Supplements & ER

Answer 13

• Thermogenics: increased metabolic rate
• Stimulants: CV strain, increased BP
• Combined w/ caffeine and synephrine
• Contaminated w/ steroids stimulants etc