Every time you go to the doctor, they wrap a little inflatable cuff around your upper arm, pump air into it, and squeeze your poor little bicep until it just about explodes. They're measuring your blood pressure, but how does it work?

The air is pumped until your circulation is cut off (you know, that uncomfortable feeling). When they place a stethoscope under the cuff, they can't hear anything. Then as the air is slowly let out of the cuff, blood begins to flow again and they can hear your blood pulsing.

This is the point of greatest pressure (called Systolic), and is usually expressed as how high it forces a column of mercury to rise in a tube (that's why they look at that little dial). 120 mm is about normal.

Then, as more and more air is let out of the cuff, the pressure exerted by the cuff is so little that the sound of the blood pulsing against the artery walls subsides and there is silence again. This is the point of lowest pressure (called Diastolic). 80 mm is normal.

Normal blood pressure is 120/80 (systolic/diastolic) or less. When both numbers start to go way up, you've got high blood pressure.

If you want to know why high blood pressure is called the "silent killer," then

Nearly 1 in 3 adults has high blood pressure, and there are no symptoms, so about 1/3 of them don't even know it. If you have high blood pressure, you could be at risk for having a stroke, heart attack, heart failure, or kidney failure. Yikes.

You may have high blood pressure because of your genetic make-up, stress or nerves (that's why they often take it again at the end of your appointment when you're more relaxed), obesity, diabetes, excessive alcohol use, or too much sodium in your diet.

Fit's Tips: I hate to sound like a broken record, but exercising, losing extra weight, and eating healthy are great ways to get your blood pressure under control. If you've done all this and your blood pressure is still high, your doctor may prescribe medication to lower it.