Just remember the heart is a pump. It attempts to pump the demanded volume of fluid by using a combination of Speed (Heart Rate) and Pressure (Blood Pressure). A heathy heart will only pump the required volume of blood, no more and no less. It will vary the HR and BP in coordination to deliver that volume. An unhealthy pump whether by disease or poor maintenance will give skewed readings as it attempts to do its' job, but can't.

So, HR by itself doesn't mean a lot. Nor, does BP by itself. Factor in any electrical circuitry or mechanical problems from the birth process and numbers produced may mean even less.

Hear rate and stroke volume (the heart is a displacement pump).

Absolutely, that is what I said, but in layman's language. The heart only has two tools to work with Rate and Pressure.

In what way is blood pressure equivalent to stroke volume? It should be obvious that the two are different just by looking at the units. The first is measured in force per unit area and the second as volume or length cubed.

Think of it this way, keep heart rate and stroke volume the same - will the amount of blood circulating change with the elasticity of the heart or diameter of the aorta?

Oh, we are going off on a related technical subject, eh? I never said it was the equivalent. Although the heart has only Rate and Pressure to work with stroke volume, of course, is affected by external factors such as Preload, Contractile Force and Afterload. So, although it is true that the ultimate technical stroke volume is the result of all the forces for this sub-set discussion on the heart alone it is Rate and Pressure.

The OP and subsequent discussion focused on Heart Rate as a reflection of fitness. That is where I'm focusing my comments.

age 64, measured RHR just now after drinking two cups of coffee, 56 bpm. Wonder what it was before the coffee. May measure it when i wake.

+1...............when low is too low.

I should have put in the smiley.