Decrease in Heart Rate during exercise

I have recently started working out at the gym a couple of times a week. Today I had been on the eliptical for 20 min then I got on the treadmill. My heart rate was 145 on the eliptical and stayed that way for the first couple of minutes on the treadmill. Then I noticed that my hr went down to 50. I adjusted my grip on the bar but it didnt change. My heart rate did increase up to 70. This happened once before but I thought  it was the machine. I had my friend check my pulse while I continued on the treadmill and she got 78. I did not feel well and I still dont. Just wondering what could have caused the drop in my heart rate while exercising.


This discussion is related to PVC's.

[kenkeith]

It could be vasovagal syndrome effecting parasympathetic nervous system (vagal tone) and that will effect hemodynamic (blood pressure and heart rate) responses.

This results in a spectrum of hemodynamic responses:

On one end of the spectrum is the cardioinhibitory response, characterized by a drop in heart rate (negative chronotropic effect) and in contractility (negative inotropic effect) leading to a decrease in cardiac output that is significant enough to result in a loss of consciousness or lighheadedness. It is thought that this response results primarily from enhancement in parasympathetic tone.

On the other end of the spectrum is the vasodepressor response, caused by a drop in blood pressure without much change in heart rate. This phenomenon occurs due to vasodilation, probably as a result of withdrawal of sympathetic nervous system tone.
The majority of people with vasovagal syncope have a mixed response somewhere between these two ends of the spectrum.