Let's assume that you are indeed having Supra Ventricular Tachycardia episode (please understand that we have no way of knowing). SVT can be initiated at any time; not just by exercise. In fact, as I aged, my lifelong SVT happened more while at rest than under heavy physical demands. As a kid running, skating, and cycling were the kind of activities that would get it going. As I got older, I would experience SVT driving my car, eating a meal, or perhaps just watching television.