High Levels of Intense Exercise May Be Unhealthy for the Heart (image) Elsevier Health Sciences Share Print E-Mail Caption Increased incidence of arrhythmias in the athlete's heart. There is a well demonstrated association between atrial fibrillation and/or flutter and endurance exercise training. There is also an increase in premature ventricular beats, although this tends to be benign in most athletes. Although there is some speculation that extreme exercise might cause serious arrhythmias in some cases, these events remain very uncommon. PPM, permanent pacemaker; RV, right ventricular. Credit Canadian Journal of Cardiology Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.