Part 1: potential dangers of extreme endurance exercise: how much is too much? Part 2: screening of school-age athletes.

The question is not whether exercise is or isn't one of the very best strategies for improving quality of life, cardiovascular (CV) health and longevity-it is. And there is no debate as to whether or not strenuous high-intensity endurance training produces an amazingly efficient, compliant, and powerful pump-it does. The essence of the controversy centers on what exactly is the ideal pattern of long-term physical activity (PA) for conferring robust and enduring CV health, while also optimizing life expectancy. With that goal in mind, this review will focus on the question: "Is more always better when it comes to exercise?" And if a dose-response curve exists for the therapeutic effects of PA, where is the upper threshold at which point further training begins to detract from the health and longevity benefits noted with moderate exercise? The emerging picture from the cumulative data on this hotly debated topic is that moderate exercise appears to be the sweet spot for bestowing lasting CV health and longevity. However, the specific definition of moderate in this context is not clear yet.