Over the past two months I have been doing a lot of reading about "Heart Rate Variability", the variation in beat-to-beat intervals of the heart.
Prior to that, I knew that most athletes had a lower resting heart rate than sedentary folks; however I had assumed that a resting heart rate was strong and steady - That is absolutely NOT the case.
A healthy heart has a great deal of variability (oscillating up and down with inhalation and exhalation) and exercise tends to improve (increase) HRV unless you are in an overtrained state.
Just thought I would pass this along since it was new information to me.
I read on Art DeVany's site a long time ago that the heart beats steadily like a metronome on two occasions: during long-distance running and right before cardiac arrest. Hrmmm..
You lousy kids! Get off my savannah!