What you really need is faster cardiac output. By exercising for long periods, you actually induce the opposite response. When you exercise continuously for longer periods of time, your heart has to become more efficient. Greater efficiency comes from "downsizing." You give up maximal capacity because smaller can go further.

A recent Harvard study examined middle-aged men, exercise, and cardiovascular health. Researchers found that men who performed repeated short bouts of exercise reduced their heart disease risk by 100% more than those who performed long duration exercise.

In an article by Al Sears, M.D., titled "Aerobics is Dead!" he states: "The biggest mistake of the 1980s is finally over and done with. Jumping around for 45 minutes to an hour won't boost your lung capacity, it won't strengthen your heart -- it won't even help you lose weight. Even worse, aerobic training -- the kind most doctors and even the federal government tout as the path to good health -- can actually wreck your body. Do enough, and aerobics will make you sick, tired and old before your time."
If you only exercise within your current aerobic limits, you do so without improving your aerobic capacity. In other words, you never push hard enough to stop to catch your breath. This kind of aerobic exercise trains your body for endurance and efficiency.

That sounds great, right? But this kind of "logic" causes "shrinkage:" Smaller muscles, smaller heart and smaller lungs. What's worse, it wipes out your heart's and lung's reserve capacity.