Encyclopedia of Health and Medicine

A
aerobic fitness The efficiency with which the
cardiovascular system functions to meet the oxygen
needs of cells throughout the body, particularly
under the increased pressure of intense
physical activity or exercise. The higher a person’s
aerobic FITNESS LEVEL, the more air the LUNGS can
take in each breath, the more oxygen that enters
the BLOOD, and the more blood the HEART can eject
with each contraction. The outcome is that the
cardiovascular system can deliver higher concentrations
of oxygen to body tissues with less effort,
which increases ENDURANCE. Aerobic fitness is a
key measure of cardiovascular health.
ACTIVITIES THAT IMPROVE AEROBIC FITNESS
aerobic dance basketball bicycling
canoeing cross-country skiing handball
hiking ice skating jogging
kayaking racquetball roller skating
rowing running shooting hoops
snowshoeing soccer spinning
squash stair climbing stationary cycling
step aerobics swimming tennis
treadmill volleyball walking
Physical activities that exercise the muscles to a
level that increases the HEART RATE and BREATHING
rate for a sustained time of 15 minutes or longer
provide an aerobic workout for the body that
strengthens cardiovascular efficiency and
improves aerobic fitness. Consistency is the key
to aerobic fitness. Health experts recommend aerobic
activity three to four times a week, ideally in
sessions that are 30 to 45 minutes long. The
higher a person’s aerobic fitness level, the easier it
is to sustain aerobic activity for longer periods of
time.
See also AEROBIC CAPACITY; AEROBIC EXERCISE;
AGING, CARDIOVASCULAR CHANGES THAT OCCUR WITH;
CONDITIONING; EXERCISE AND HEALTH; LIFESTYLE AND
HEALTH; MUSCLE; PHYSICAL ACTIVITY RECOMMENDATIONS;
PHYSICAL EXERCISE AND CARDIOVASCULAR HEALTH;
WALKING FOR FITNESS.
aging, cardiovascular changes that occur with
The most significant age-related changes in cardiovascular
function occur at birth in both sexes and
with MENOPAUSE in women. Though changes in
METABOLISM occur with aging that affect all body
systems, researchers now believe cardiovascular
health does not inherently decline simply as a
function of aging. DIABETES, OBESITY, lack of physical
exercise, and cigarette smoking are the leading
causes of acquired CARDIOVASCULAR DISEASE (CVD)
among adults. The effects of these factors are
cumulative; they are more likely to result in disease
the longer they exist and the more of them
are present. Accordingly, the risk for acquired cardiovascular
disease increases with age because as
people get older they tend to develop health conditions
that set the stage for cardiovascular deterioration.
Most researchers believe these risks are
mutable (changeable) through lifestyle.
Cardiovascular Changes at Birth
The cardiovascular system is among the first body
systems to develop in the EMBRYO, with the rudimentary
HEART beginning to beat at three weeks
gestational age. The heart fully forms, and a rudimentary
circulatory network develops and functions,
by eight weeks gestational age. Before birth,
the FETUS draws its oxygen supply from its
mother’s BLOOD supply, in an exchange that takes
place across a membrane in the PLACENTA (fetal
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