Your resting heart rate at 40 is a window into your health at 60.

But most people don't pay attention to it or know how to track it.

Here's what it tells you and how to lower it: Resting heart rate (RHR) is how many times your heart beats per minute at complete rest.

A lower RHR means your heart is more efficient. It moves more blood per beat, less effort per contraction, less cumulative strain over decades.