As you can see in this diagram, during the contraction (blue line), the blood flow has virtually stopped. This means that no oxygen and no nutrients are reaching the muscle cells. However, when the contraction has stopped (dashed line), perfusion is immediately restored. In fact, for some time, it is even stronger than normal, in order to replenish the oxygen shortage in the cells and to get rid of the accumulated waste. This is called ‘reactive hyperaemia’ (reactive = reaction to the contraction; aemia = blood and hyper = more).