The heart is actually one big muscle. But it is a specialized muscle and different from the other muscles that are attached to your bones. Where you have to purposefully make your arm or leg muscles move, the heart muscle is continuously and, hopefully, efficiently pumping away, day and night without you thinking about it. 

The purpose of this non-stop pumping action is to force oxygen rich blood to flow throughout the body. As a muscle, it too needs oxygen and this is supplied to the heart muscle itself by way of the coronary arteries that lie on top of and within the heart muscle.

If the average heart beats 80 times a minute, that would be 4,800 times in an hour, 115,200 times in a day, and 40,550,400 times in a year. That's a lot of work. Can you imagine pumping your biceps with that type of regularity? Doesn't the heart have to rest? Technically, in between each beat there is a moment of rest. You might say the average heart then rests 80 times a minute, and so on.

Measuring one's blood pressure is essentially measuring the maximum force of the heartbeat or contraction of the heart muscle, known as SYSYOLE, and the minimum pressure of the heart after a contraction during relaxation, known as DIASTOLE. Everyone is familiar with these numbers being represented with one top of the other, like 120/80 (one twenty over eighty). The numbers themselves were derived from actually hooking up an artery to a column of mercury and watching how high the heartbeat forced the mercury with the height measured in millimeters of mercury.

Blood pressures that are higher than 120/80 pose a problem. Now that you know what the top number represents (the force with which the heart has to beat to get the blood to flow through the body), you might begin to see that the increased force could actually be harmful to the rest of the vascular system and other body organs like the brain, kidneys, and the heart itself. And, hopefully you can begin to understand that the increased pressure during the time when the heart is supposed to be at rest between beats probably is not too good either, for the heart or the rest of the vascular system.

Exercise strengthens the heart muscle just as exercise strengthens other muscles of the body. A well-exercised, well-tuned heart does not have to beat 80 times a minute. It can beat less frequently while still supplying sufficient force to accommodate circulation. A well-exercised, well-tuned heart is strong enough with each heartbeat that it can accomplish the same task of circulating the blood but at lower pressures; a well-exercised heart is an efficient heart.

Do you know what your blood pressure is?

• Agnes Oblas is an adult nurse practitioner with a private practice and residence in Ahwatukee Foothills. For questions, or if there is a topic you would like her to address, call (602) 405-6320 or email Her website is

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