There is typically 5 litres per minute circulating in the cardiovascular systems at rest, approximately 20% of the blood flows to the muscle tissue. The remainder of the blood circulating in the body is utilised by the heart, brain, skeleton, skin and gastrointestinal tract (the liver and kidneys).
Blood Flow Distribution during Exercise
Organs like the brain and heart can’t compromise their blood supply and actually see an increase in supply volume during exercise. When exercising the body will divert blood away from less active tissue to active muscles, the heart and finally the skin for improved thermoregulation. Although cardiac output will only increase by 3 to 5 times the resting level, the working muscles will see an increase of nearly 20 times of blood supply during exercise.
Blood Distribution Differences Between Rest and Exercise
|Blood Distribution During Rest||Blood Re-Distribution During Exercise|
|Kidneys||22% (1100ml)||1% (250ml)|
|Liver||27% (1350ml)||2% (500ml)|
|Muscle||20% (1000ml)||83.9% (21000ml)|
|Heart||4% (200ml)||4% (1000ml)|
|Skin||6% (300ml)||2.4% (600ml)|
|Brain||14% (700ml)||3.6% (900ml)|
|Other||7% (350ml)||3.12% (780ml)|
Exercise will cause an increase in the haemoglobin values of blood, the component that transports oxygen. The capillary density, size and fibre ratio will also increase to allow a more efficient diffusion between the blood vessels and working muscles.
During exercise blood flow is redistributed to the working muscle tissue to maintain performance. As the blood is redistributed, the cardiac output increases to approximately 25 to 30 litres per minute. During high intensity exercise the muscle tissue will receive 80 to 85% of the total cardiac output.