There's no question that exercise triggers premature contractions. I find that it's not so much light cardio that does it, but more resistance and weight training that triggers it for me. But again, the PACs and PVCs never lead to anything, and always die down in a couple of hours. I totally relate to your feeling of having to get up and move around. I would say keep doing what you're doing and don't let fear interfere, and keep your cardiologist informed about what you're experience. You need to stay active for general heart health.