Cardio activity should be about building lung capacity NOT endurance. In order to "go the distance", one needs to store fat to complete the exercise. -- In the past I trained for a marathon. Now I need a steady, day-to-day activity that allows me fitness health for the long haul--the next 30 years!!
Taken from the book: P.A.C.E. the 12 minute Fitness Revolution, by Dr. Al Sears.