Heart slows during heavy exercise

During interval training, is it normal for the heart rate to reduce during the high intensity part?

My experience:   During interval training,
1. the heart rate slowly increases during the high intensity part,  e.g. 140-150bpm over 30 seconds
2. then the heart rate quickly increases during the 1st part of the low intensity (or rest),  150-170 over 10 seconds
3. then decreases during low intensity period,  170-150 over 50 seconds,
4. then nearly instantly decrease to 140bpm during the next high intensity part.

[Michael J. McWilliams, M.D.]

During interval training, is it normal for the heart rate to reduce during the high intensity part?

My experience:   During interval training,
1. the heart rate slowly increases during the high intensity part,  e.g. 140-150bpm over 30 seconds
2. then the heart rate quickly increases during the 1st part of the low intensity (or rest),  150-170 over 10 seconds
3. then decreases during low intensity period,  170-150 over 50 seconds,
4. then nearly instantly decrease to 140bpm during the next high intensity part.

I think the real question is do you have symptoms because of this -- if you do not, I would not worry about it.  Mention it to your doctor and if your EKG is fine and you have no symptoms while this is happening, it is not a problem.  

Typically the heart rate will increase during high intensity periods.  It will sometimes decrease if you maintain the same level of intensity as your body meets the acute demands and then reaches a steady state that does not require as high of a heart rate. There is a chance that your heart rate is dropping some beats at faster rates -- this is a well known normal physiologic principle as the long as the heart rate is reasonable for your age and there are no symptoms.  The only way to know for sure what is happening is to see it monitor like an exercise stress test.

I hope this answers your question.  Thanks for posting.