Question: why does our heart beat when we run

Duane Mellor answered on 19 Nov 2014:

Our heart beats faster when we run as the muscles require more oxygen and fuel. Increased heart rate can increase the flow of blood and nutrients and oxygen to and removing waste away from working muscles. Also if we are competing in a race we may release adrenaline (Americans called it ephedrine) which is a flight or fight hormone, this will increase heart rate and may help us run faster too