Question

Imagine you had to engage in extreme physical exertion—say, running a few miles or doing a lot of sit-ups. What will happen to your heart rate? Why does your body need to change the way it behaves?

Please make it super short and simple

Answer 1

During extreme physical exertion, your heart rate increases to pump more blood and oxygen to your muscles. This helps meet the higher energy demands of your body. Your body changes its behavior to keep you moving and to remove waste products like carbon dioxide.