The Rate of Perceived Exertion (RPE)
In this six-week program, you can gauge your intensity using the Rate of Perceived Exertion and/or a percentage of your maximum heart rate. Here's what the numbers mean:

1-2
%MHR: 20-30
Intensity: Very easy; you can converse with no effort.

3
%MHR: 40
Intensity: Easy; you can converse with almost no effort.

4
%MHR: 50
Intensity: Moderately easy; you can converse comfortably with little effort.

5
%MHR: 60
Intensity: Moderate; conversation requires some effort.

6
%MHR: 70
Intensity: Moderately hard; conversation requires quite a bit of effort.

7-8
%MHR: 80
Intensity: Difficult; conversation requires a lot of effort.

9-10
%MHR: 85-90
Intensity: Peak effort; no-talking zone