I always experience PVC's after exercise. It usually doesn't happen until 3-5 hours after I am done exercising, but it always happens! I've asked my cardiologist about this and he hasn't heard of it. It makes me think that doing cardio isn't good for my heart. I use to be a runner and refuse to run because I can't handle the aftermath.
If I experience them during exercise, it is usually during running typically sometime after mile 7 or 8. It just depends. Sometimes I start experiencing them as early as mile 2. They occur in strings, and usually stop when I stop. They may restart if I restart. On occasion, they are bad enough that I must stop. However, on other occasions I may not get a single one.
I also experience PVC's at rest, for no apparent reason (although less frequently).
PVC's in a structurally normal heart are not dangerous during OR after exercise. Neither occurrence means anything more than the other.
For the record though, I experience most of my exercise related PVC's AFTER the physical activity is over. Go figure!!!