Cardiac output (CO) is the term used to describe the volume of blood pumped out by the heart over a minute. It worked out by multiplying the number of heartbeats per minute (bpm) by the stroke volume of the heart. The healthy human adult at rest has a cardiac output of between 4 and 7 litres/min, but this can rise to as much as 30 litres/min during exercise; it is controlled as to the oxygenation requirements of the body. Regulation is achieved by hormones, the autonomic nervous system, and by the heart itself. A low cardiac output, especially during exercise, can indicate that heart damage has occured, or that there has been a significant loss of blood.