After walking on a treadmill for about an hour at 3 MPH, I usually get the urge to use the bathroom, but while urinating my heart rate suddenly spikes above 200 BPM. All the other times that I use the bathroom, this doesn't happen. It only happens specifically after walking for an extened period of time ont he treadmill. I've consulted with a cardiologist in the past about this issue. The cardiologist had me do a stress test and use a holter monitor for 24 hours to track my heart rate, but those results came back normal. What should I do?