A normal heart rate is 60-100 beats a minute. Having said that, people who do heavy exercising can have a heart rate of 40 and still be perfectly healthy. The more in shape you are, the slower the heart rate can be and you can still be healthy as far as the heart goes. Thelower heart rate can also be a result of what you are doing; when you sleep, your heart rate can drop down into the 40's range with no ill effects. What IS importantant is whether or not your heart rate will increase with activity. If you are working hard, say running, and your heart rate will NOT go above the 100 range, it's time to visit your doctor.
Oh okay. Thank you very much!
One of the best measures/tests is 'how do you feel"? If you feel a shortness of breath or have problems with dizziness or head aches the 50 (resting) HR may be too low, if not, you have a very good cardiovascular system. Like blood pressure, lower is better if it doesn't cause any of the above or similar symptoms.
If you have any troubling symptoms, such as the list above, you should discuss with a doctor. A resting HR much below 50 should be checked by a doctor even in the absence of troubling symptoms, I believe.