The process of redistributing blood during excercise

When we exercise it causes an increase in the heart rate. This creates a change in the concentration of O2 and CO2 in the blood and the respiratory system is able to detect this change and increase the rate in which we breathe.
The intercostal muscles of the diaphragm allow the thoraxic cavity to expand, enabling more air to be drawn in. This allows the diffusion of gases to be more efficient and the transportation of gases increases due to increased blood flow.

During exercise the heart rate increases rapidly. This provides the muscles with the necessary oxygen and nutrients to provide the muscles with energy. During exercise, cardiac output is increased.

During exercise stroke volume increases because, more blood is being sent back to the heart due to the muscles squeezing blood in the veins. The heart fills up with more blood and it stretches. This stretching allows the muscle fibres to contract more strongly and therefore more blood is being pumped out.