Exercise and the heart: can you have too much of a good thing?

Reports that participation in prolonged exercise can lead to a transient depression in ventricular function and/or a minor increase in biomarkers of cardiomyocyte insult have stimulated significant media and scientific attention in the last few years. Despite being of relevance to the scientist, the clinician, and a broad spectrum of athletes, these phenomena are poorly defined and controversial. Specifically, the definition and the description of these topics are quite limited, and conflicting data are available. Further, the mechanisms underpinning these events are not clear. Finally, a clear message related to the short- and the long-term impact on cardiovascular health and/or sports performance is lacking. The symposium "Exercise and the heart: Can you have too much of a good thing?" was presented at the ACSM Annual Meeting in New Orleans on June 1, 2007 to specifically address these issues. This initial introduction sets out the background to the main articles that will document our current understanding of these problems as well as suggest important avenues for further research.