The current standard for anyone with an implanted defibrillator is that they should avoid participating and competing in intense sports of any kind, but the younger the patient the less compliant they often are. And with more and more younger patients getting ICDs (implantable cardioverter defibrillators) it's becoming more and more important to get a clear understanding of exactly how the devices are affected by physical activity. As of now doctors warn against playing in sports just because they have no idea how strenuous exercise, adrenaline, and physical jolts/impacts can affect defibrillators. They assume it's all risky, but they really don't know for sure, which is prompting new research. Seems like this is a quality of life issue, really. Taking care of yourself is important, but that usually means at least some physical activity, doesn't it?
