A test performed to detect the presence of myoglobin in urine. Myoglobin is an oxygen-binding protein found in cardiac and skeletal muscle. Exercising muscle uses up available oxygen as it metabolizes available fuel (that is, glucose and fatty acids) for energy. The presence of myoglobin in muscle provides an extra reserve of oxygen so that exercising muscles can maintain a high level of activity for a longer period of time. When skeletal muscle is damaged, the myoglobin is released into the bloodstream. It is filtered out of the bloodstream by the kidneys. In large quantities, myoglobin can occlude the structures of the kidney as well as break down into potentially toxic compounds, causing kidney failure .