Updated project metadata. During an episode of acute rhabdomyolysis, a microarray study identified differential expression of calcium-regulatory, mitochondrial and metabolic genes in gluteal muscle of Standardbreds. Whether this represents expression related to acute myodegeneration or a specific molecular signature of susceptibility to recurrent exertional rhabdomyolysis (RER) is currently unknown. We compared gluteal muscle histopathology, gene/protein expression and antioxidant concentrations between Standardbreds with a history of, but not currently experiencing rhabdomyolysis, and race-trained controls to derive a molecular susceptibility profile.