ResplendentDaylight t1_j6f58py wrote

Your blood vessels are like roads. Without exercise they are dirt roads. They get potholes, travel across them can be cumbersome and difficult.

When you start exercising, your body starts to patch up those potholes. Maybe add some cement or tar to help the roads be a bit more stable.

With lots of aerobic exercise, your roads becomes highways, well developed and cleaning moving with lots of chill traffic that doesn't cause accidents because of the conditions they are driving in.