Encyclopedia of Health and Medicine

A–B
aerobic capacity The maximum amount of oxygen
the body can extract from ambient air (the air
of the normal environment) and use during physical
activity, expressed as VO ˙ 2max in terms of milliliters
of oxygen per kilogram of body weight per
minute (mL/kg/min). Because men have larger
LUNGS and thus greater surface area for oxygen
exchange, all other factors being equal men have
greater aerobic capacity than women. Higher
VO ˙ 2max correlates with increased ability to sustain
high-intensity exercise for an extended time, such
as during ENDURANCE activities. People who participate
in athletic events at a competitive level, amateur
or professional, typically have higher aerobic
capacity in general and a significantly higher
VO
˙ 2max in the activity of specialty such as bicycling,
cross-country skiing, distance running, and
swimming. Aerobic capacity is a key indicator of
cardiovascular fitness.
REPRESENTATIVE AEROBIC
CAPACITY MEASUREMENTS (VO ˙ 2MAX )
sedentary woman 38 milliliters per kilogram per minute
(mL/kg/min)
aerobically fit woman 60 mL/kg/min
sedentary man 42 mL/kg/min
aerobically fit man 80 mL/kg/min
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Researchers believe the foundation of aerobic
capacity is genetic; some people are born with
greater aerobic capacity potential, and with sustained
AEROBIC EXERCISE at a competitive level they
are able to maximize that potential for high
VO ˙ 2max . A sedentary (physically inactive) person
who undertakes a planned, progressive program
of aerobic exercise can often improve his or her
aerobic capacity by 20 to 30 percent. Such
improvement is significant from a health perspective
because there is a strong correlation between
low aerobic capacity and increased risk for CARDIO-
VASCULAR DISEASE (CVD). Increasing aerobic capacity
consequently lowers CVD risk factors.
Direct measurement of VO ˙ 2max is fairly complex;
because of this doctors tend to conduct direct aerobic
capacity testing only in people who have pulmonary
disease. A pulmonary function testing
center conducts direct VO ˙ 2max measurement, for
which the person runs on a treadmill or rides a
stationary bicycle wearing specialized equipment
that measures the exchange of oxygen and carbon
dioxide. Calculations using the measurements
determine the VO ˙ 2max , usually along with other
measures that provide a detailed perspective of
lung function and lung capacity.
There are several methods for indirectly measuring
aerobic capacity, all of which involve performing
sustained aerobic exercise such as
running or walking for a determined period of
time or a known distance. Calculations use the
information to project the anticipated VO ˙ 2max for
the data. Indirect VO ˙ 2max measurement is less precise
than direct VO
˙ 2max measurement but is accurate
enough for most people who are engaged in
aerobic exercise and want to know, or monitor
improvements in, their aerobic capacity.
See also FITNESS LEVEL.
aerobic exercise Physical activity that raises the
HEART RATE to 60 percent of maximum heart rate,
called the target heart rate, for a minimum continuous
time of 20 minutes.
A general guideline for approximating one’s
target heart rate is the “talk test.” At target heart
rate, a person should be able to speak. A person
who cannot talk during exercise is likely exceeding
his or her target heart rate and is working too