Cardiac output describes the volume of blood pumped out of the heart per minute

  • It is roughly 5 litres per minute in a typical human adult at rest (it increases to ~25 L/min during heavy exercise)

Blood is distributed to body organs according to physiological requirements and this distribution changes with exercise:

  • Blood flow to the brain is largely unchanged during exercise (brain is vital and hence blood flow cannot be altered)
  • Blood flow to the heart wall, muscles and skin is increased (to facilitate improved oxygenation and heat loss)
  • Blood flow to the kidneys, liver and digestive system is decreased (due to minimal absorption and excretion)

Blood vessels will vasodilate during exercise to improve circulation and facilitate heat loss via the skin

  • This moves blood closer to the surface of the skin and is why exercise causes a person to appear flushed

Distribution of Blood Flow at Rest

blood flow