How exactly does your cardiovascular system improve from distance running over the years ?

Question

How exactly does your cardiovascular system improve from distance running over the years ?

Answer 1

Your cardio. system as a whole will not have to work as hard most of the time.  For instance say your normal resting heart rate is 65-70 right now and you don't do much in the form of exercise.  Well if you started and within 5 years from now are running 20-25 miles a week for a long time....your resting heart rate will come down tremendously, probably somewhere between 50-55.