heart rate slow down on treadmill when tired

Hi..
I started going to the gym and realized that when I feel tired on the treadmill or I am short of breath my heart beat slows to 60 to 80 beats per minute. when I am not short of breath or tired it stays up anywhere from 130 to 155 beats per minute. Is it something abnormal happening to me or  its totally normal?
I would really appreciate any info on that...

[dolfnlvr]

This result is not a normal one.  If you are excercising, your heart rate should increase.  If you have been walking/running when you suddenly feel tired and notice a drop in heart rate then you need to seek medical advice/treatment.  If you feel tired when you FIRST get on the treadmill and notice a low HR that increases with activity, then what you notice is not uncommon.  But, I don't think that is what you are describing.  It sounds to me as though you are describing a situation where you may have been walking for 5-10 minutes and suddenly feel tired and notice that your heart rate decreases dramatically.  This is cause for concern (not panic, but concern) and should be investigated by a cardiologist.

Take care, and let us know what happens.