Publisher Summary The two major energy sources for muscle contraction are glycogen and
fatty acids, whose metabolic pathways converge into acetyl-CoA for final intramitochondrial
oxidation through the Krebs cycle and the respiratory chain. Defects of substrate utilization in
muscle cause two main clinical presentations:(1) acute, recurrent, reversible muscle
dysfunction, manifesting as exercise intolerance, myalgia with or without painful cramps
(contractures) often culminating in muscle breakdown and myoglobinuria; or (2) fixed, often …