For an adult, a normal resting heart rate ranges from 60 to 100 beats per minute (bpm). For a well-trained athlete, a normal resting heart rate may be as low as 40 to 60 bpm. It has been reported Lance Armstrong has a resting rate of 32-34.
Just because one has a low heart rate does not necessarily mean that person is in good shape.
A better measurement of physical fitness is checking your heart rate after exercise and see how long it takes to get back to resting rate. This is called the recovery rate and is much more important when looking at how fit you are.
After exercising, your heart rate should drop below 120 bpm 2-3 minutes after stopping your cardio workout.