Dr. Andy Galpin

If you are fit and we improve your stroke volume,

Since the total demand, again, the back end of this equation is still 5 liters per minute, but I've increased one of the numbers, that allows me to decrease the other number.

And so your heart rate, as I said, the SA node is paying attention to many things, and one of them is that preload.

So how much blood is coming back in and how much is going back out and various other factors.

So it knows if I'm getting, say, this 100 milliliters of blood out per pump,

I don't have to pump as often, so increase the acetylcholine drive, slow the heart rate down, and let's chill out.

In fact, we'll cover some of these numbers later about what a good heart rate is, what the best we've ever seen, why you don't want to be too high or too low, and stuff like that.

But that's basically what's happening.

And so we can identify whether or not we're struggling in either the stroke volume portion, the cardiac output side of the equation, or heart rate just based on that understanding of how the heart works.

That will then tell us what style and type of training we need to do to make the most efficient improvements in not only our heart rate, but more importantly, our VO2 max.

Now, your heart rate, again, how many beats per minute you're using at rest or during exercise, is incredibly telling.

As I mentioned earlier, it doesn't actually change, though, in response to exercise training at its maximum.

The only really thing that matters in this particular case is your age.

And we know that maximum heart rate goes down as you get older, but it doesn't alter that much with fitness.

And so...

What it can tell you, though, are things like your heart rate variability.

And so let's just use the example of a heart rate of 60 beats per minute.

So one would think and assume that if my heart rate is 60 beats per minute, that means I'm having 60 beats in 60 seconds.

That would be one beat per second.

And if you calculated the total amount of beats you had over the course of the minute, you would in fact achieve 60.