What do blood pressure numbersmean?
Blood pressure is a measure of how much
the blood presses against the walls of the
arteries. This creates two forces: The first
comes from when the heart pumps blood
into the arteries; the second is the force of
the arteries to resist the blood flow. When
a person “takes a blood pressure,” he or
she is taking a ratio: The higher number
(called the systolic or top number) repre-
sents the pressure when the heart con-
tracts to pump blood to the body; the
lower number (called the diastolic or bot-
tom number) represents the pressure
when the heart relaxes between beats. For
example, for a blood pressure of 120/76
(said, “120 over 76”), the systolic reading
is 120 and the diastolic reading is 76.
In actuality, the numbers represent
how high the blood’s pressure would
force a column of mercury to rise in a
tube. For example, a systolic reading of 120 means the mercury would rise 120 mil-
limeters (usually labeled mm Hg, with Hg the symbol for mercury) in a tube. Based on
the most recent information (and it keeps changing), a blood pressure below 120/80 is
considered optimal for adults; 120 to 139 over 80 to 89 is considered “prehyperten-
sion.” Anything over 140/90 is considered hypertension, which includes three stages,
with the highest hypertension reading, stage 3, being anything above 179/109.How does one calculate resting heart rate?
Calculating resting heart rate (RHR) involves easy math. It is the number of heart beats
per minute when the body is resting, with the beats per minute representing the num-
ber of times the heart contracts. To measure the RHR, just count the number of beats
per minute via the pulse—usually taken either on the inside of the wrist or along either
side of the neck—for 15 seconds. Then multiply this number by four (15 4 60 sec-
onds) to get the heart rate per minute. Or count for 10 seconds, then multiply this
number times six (6 10 60 seconds) to get the heart rate per minute. For example,
if you count 12 beats in 10 seconds, multiply 12 by 6 to get a resting heart rate of 72.How does one calculate heart rateduring exercise?
One reason to calculate heart rate during exercise is to know if a person is getting ben-
406 eficial exercise to keep the heart and body healthy. In order to determine the safe and
When a nurse or doctor takes your blood pressure,
the two numbers they read to you indicate systolic
and diastolic pressures in your arteries. Hulton
Archive/Getty Images.