Myoglobin is a small oxygen-binding protein found in heart and skeletal muscles. The function of myoglobin is to trap oxygen within muscle cells, which allows them to produce the energy required for muscular contraction. When heart or skeletal muscle is injured, myoglobin is released into the blood, and increased concentrations can be measured within a few hours following injury. INCREASED levels in the serum are an early marker for myocardial damage, i.e. myocardial infarction. Increased levels are also seen after heavy exercise (e.g. marathon running), skeletal muscle damage (physical injury, rhabdomyolysis and muscle disease) and severe renal insufficiency.