Have you been to the doctor recently? What was your RHR then? Just because I have a low RHR now, doesn't mean I haven't worked on my aerobic fitness a lot and it is much better. Another test that a doctor told me about was getting my heart rate up to about 20 from my max heart rate using the 220 - age theory on a treadmill running and keep it there for a minimum of five minutes and then go from running at 7.5 mph down to a 3 mph walk. What is my HR after 60 seconds and 90 seconds. He told me that if I drop over 30 beats in that time frame I have a decent cardio system. This is not a science, and I am not a doctor. This is just me.

If you really want to know more, talk to your doctor and see what they want you to do and where you should be.