Fight, Flight and Fright

The focus of tonight’s presentation is stress and exertion. When faced with a threat like the approach of a predator, a human’s natural response is to turn and flee. Yet a soldier facing enemy guns can choose to stand and fight. Such a decision and the subsequent physical work required involves burning a huge amount of energy. So how does the body deliver such a large amount of energy so rapidly? What happens to the heart, lungs and blood vessels used to transport the energy, and how is it used once it is delivered?