My memory has just told me that Miguel Indurain, legendary Spanish cyclist, was infamous for a ridiculously low resting heart rate. To confirm my suspicions I did a google search and came up with this:
"The heart is a pure powerhouse muscle. It responds to exercise the same way an ordinary muscle does. We can make it more powerful or we can let it get scrawny and weak. "When you hold a human heart in your hand, it feels like a piece of filet mignon," says Michael Crawford, M.D., Chief of Cardiology at the University of New Mexico Health Science Center. "Only it's hollow, so it gives a little more when you squeeze it, but it's basically just muscle."
NOTE: An average heart weighs 300g (10.7 ozs.) and is about the size of a fist.
The average resting heart rate is 66/72 beats per minute (bpm). A well-trained endurance athlete is 40 bpm. The lowest on record is 28 bpm (Miguel Indurain, a Spanish cyclist). My resting heart rate is 38 bpm.
Paul D. Thompson, M.D., Professor of Medicine at the University of Pittsburgh and Director of Preventive Cardiology indicates, "A slow heart rate is absolutely beneficial for health, in fact, there are about nine studies showing that people with the slowest heart rates live the longest."
A well-trained heart can be 30 to 40% larger than a normal heart and pump 50% more blood with each beat.
According to Dr. Crawford, " You can demonstrate significant changes in heart strength in four to six weeks." A strong heart is like buying life insurance. The required premium is REGULAR installments of CARDIOVASCULAR EXERCISE."
(see http://www.fitness-sergeant.com/heart.htm)