Rapid rise and drop in heart rate during exercise

[robinruth]

I am 55 and about thirty-  maybe even forty-pounds overweight. My resting blood pressure is usually around 110/70. Normally when I exercise (about 5X per week) I use the elliptical machine for a thirty minute workout. No matter how hard I push, it is hard for me to get my heart above 120. However, I have lately started using the treadmill (inclined and at a speed of about 4.0 miles per hour) and when I place my hands on the heart monitor gauges my heartrate is shown as 220, then 200, then 190, 180, 170, etc--dropping rapidly-until it settles at about 100. This has happened repeatedly. It happens when I go on the treadmill first and start there or when I go on it after I have been on the elliptical. It has also happened once or twice in the middle of my thirty minute workout just on the treadmill. I don't feel physically stressed. I thought it might be the treadmill machines but I have tried them all and still had this happen. My friend I exercise with  uses the treadmills too and she doesn't experience any of these kinds of rapid changes. So it is not he machines. Should I be worried?
Thanks for the advice!

[kenkeith]

It would be difficult to calculate the exact normal parameters for you, but blood pressure and pulse rate compensate for the paring results to make sure an individual gets adequate oxygen.  When your blood pressure is low, your body raises the pulse rate to push more oxygen through.  When your blood pressure is high, your body lowers the pulse rate to prevent too much oxygen from being in your system.  It creates a balance in your body to maintain homeostasis.

You start with a low blood pressure and with aerobic exercise the system will compensate with higher pulse rate. As the exertion progresses the blood pressure will rise and heart rate will decrease. Alsoi, it is said exercise reduces stress and that may have neurological effect as well.   It would be difficult to determine equilbrium of vital factors (PR and BP) regarding optimum oxygenated blood flow and at what level of exertion. Additionally, you may be on medication that prevents your heart rate to be higher than than 120.  I take a beta blocker that almost prevents a heart rate greater than 120.

[robinruth]

Thank you for your note. I think I'll have a stress test done by the DR when I get back from vacation in a few weeks just in case there is something wrong. I have a lifelong history of arrhythmia that has never kept me from anything, but my older brother just had surgery for his. I read about your struggles and wish you very well! Robin

[Jerry_NJ]

You need to verify the HR numbers, use you finger and a stop watch (second hand on a clock) and get your HR that way.  If it doesn't confirm the machine reading, the machine is wrong and you are doing something or have some grip characteristic that it doesn't handle well.  

If you feel alright, you likely are and the machine given a false reading.