I've recently been having this strange feeling of shortness of breath up to 4 or 5 hours after i get done with moderate intensity medium to long runs (8-10 miles for me). I've had the feeling before back in high school and it seemed usually to occur when i was stepping up milage or the average pace of my milage. This time it's started after i'v started picking up the milage and intensity again after a few easy weeks. i feel great on my runs and the sensation i'v described is particularly uncomfortable or worrisome, but it is noticeable. can anyone tell me if its normal to feel short of breath that long after a run or is there something else going on?