2. A more basic science study from Dr Mont's group in Barcelona also suggests  those with a history of arrhythmias following endurance training may benefit from a period of "deconditioning" following their efforts. The suggestion follows a study in animal models that found that markers of cardiac fibrosis in rats whose treadmill exercise was followed by a period of inactivity returned to control levels. Endurance exercise causes cardiac structural changes, including atrial and right ventricular fibrosis ? and this fibrosis may play a role in the development of arrhythmias.

3. Just as inactivity after training may inhibit cardiac fibrosis in animal models, a similar study suggests that the anti-hypertensive drug, losartan, prevents the heart fibrosis induced by endurance exercise. Markers of fibrosis were reduced by administration of losartan.

SOURCE:  Papers presented to the European Society of Cardiology, June 21, 2009