Recently, exercise scientists have been concerned that there might be an upper limit to the amount of exercise and exertion that is healthy, particularly for the human heart. Now new studies indicate that too much exercise may indeed cause problems. According to a study published in The European Heart Journal in June 2013, evidence showed that rats running the equivalent of a marathon experienced cardiac muscle scarring and abnormal heart rhythms. However, related studies and data extrapolation from the Swedish study also showed that even if too much strenuous exercise promotes arrhythmia, exercise appears to lessen the possibilities of fatal heart problems. What’s more, researchers from the Swedish study note that athletic training and exercise are proven far-and-away to reduce the risk of other types of disease in humans.