effective range of exercise to get cardio-
vascular benefits, two measurements are
often taken. The first is the maximal
heart rate,a number related to a person’s
age (the heart beats slower with age). To
estimate the maximal heart rate, subtract
a person’s age from the number 220. For
example, if someone is 40 years old, his or
her maximal heart rate is 180.
The next measurement is the target
heart-rate zone. This number uses the
maximal heart rate and represents the
number of times per minute at which a
heart should be beating during aerobic
exercise. For most healthy people, the
range is 50 percent at the lower limit to
80 (some charts say 75) percent at the
upper limit of their maximal heart rate.
When a person’s heart rate reaches a
value within this zone during exercise, it
means he or she has achieved a level of
activity that contributes to his or her car-
diovascular fitness. For instance, from the above example of a maximal heart rate of
180, the beats per minute for the lower range would be 180 multiplied by 50 percent
(0.50), or 90 beats per minute; the upper range would be 180 multiplied by 80 percent
(0.80), or 144 beats per minute.
If you work out and maintain a lower-than-50- or higher-than-80-percent limit,
there are few beneficial effects from the exercise. In terms of the lower limit, the heart
is not working hard enough for any cardiovascular benefit; in terms of the upper limit
(besides the strain and injuries that can result), the heart is working too fast for any
benefit and the body can’t replenish oxygen that quickly.
What do cholesterol numbersmean?
Cholesterol numbers indicate the amount of cholesterol in the bloodstream (choles-
terol is a waxy, fat-like substance manufactured in the liver and found in all tissues).
For humans, a total cholesterol number above 200 means there is an increase in the
risk of heart disease (between 200 and 239 is considered borderline high cholesterol);
for anything below 200, there is less of a risk for heart disease.
But total cholesterol is not the only number to know. There is also Low Density
Lipoprotein (LDL), or “bad” cholesterol. LDL is the main source of the buildup and
blockage in the arteries (risk levels are above 130, measured in milligrams per 407
EVERYDAY MATH
Whenever you exercise, your heart rate increases.
Healthy exercise means not exceeding your target
heart-rate zone and maximal heart rate, which are
based on your age. The Image Bank/Getty Images.