Encyclopedia of Health and Medicine

FITNESS: EXERCISE AND HEALTH
Exercise has emerged as a significant factor in nearly all facets of health, both in terms of maintaining overall health
and in reducing risk for health conditions and injuries. A health-care practitioner who specializes in fitness-related
care may be a doctor (MD or DO), certified physician assistant (PA-C), registered physical therapist (RPT), chiropractor
(DC), or exercise physiologist. Doctors who specialize in treating injuries and conditions related to physical activity
may be board-certified in sports medicine, family practice, orthopedics, or physiatry (rehabilitation medicine). Education,
certification, and credentialing are less consistent for other fitness practitioners such as fitness trainers and athletic
trainers who primarily work outside the health-care delivery system to help individuals develop exercise regimens for
preventive or therapeutic purposes.
This section, “Fitness: Exercise and Health,” presents
an overview discussion of physical activity
as it relates to health maintenance, health risk
factors, health conditions, and preventive health
measures. The entries in this section focus on the
broad picture of how physical activity and inactivity
influence health and disease. The section
“Lifestyle: Obesity and Smoking” features discussion
and entries about fitness and exercise topics
that relate to WEIGHT LOSS AND WEIGHT MANAGEMENT.
The section “The Musculoskeletal System” contains
discussion and comprehensive entries about
the structure, function, health, and health conditions
of the bones, muscles, and joints.
Making the Connection
between Physical Activity and Health
Researchers provided the first substantive correlation
between physical inactivity and health in the
1970s when clinical and epidemiologic studies
linked sedentary lifestyle with premature death
due to health conditions such as CORONARY ARTERY
DISEASE (CAD) and HYPERTENSION (high BLOOD PRES-
SURE). Health experts subsequently issued the first
formal recommendations for incorporating regular
physical exercise into daily lifestyle as a means of
preventing the development of CARDIOVASCULAR
DISEASE (CVD). These recommendations were much
the same as current recommendations for minimal
physical activity for adults, which are
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• physical activity for a total of 30 minutes a day
at moderate intensity at least 5 days a week
and preferably every day
• physical activity for 20 minutes at a time at vigorous
intensity on 3 or more days of the week
Research has continued to strengthen the evidence
for these recommendations. However, most
Americans fall short of meeting them. The 1996
US Surgeon General’s report Physical Activity and
Health found that 25 percent of Americans do not
participate in any physical activity beyond the
requirements of daily living, and 60 percent exercise
less than the minimum recommendations for
health. Among youth between the ages of 12 and
21, about 25 percent engage in physical activity at
a level that meets minimum recommendations for
health, 50 percent participate in regular physical
activity at vigorous intensity, and 25 percent are
physically inactive.
Many adults start exercise programs and then
do not continue them, most commonly because
they begin with activities that support the FITNESS
LEVEL they want to achieve rather than those
geared to their current fitness level. Such an
approach often results in discomforts; minor
injuries such as blisters, sore muscles, and aching
joints; and discouragement because the body is
not ready for such activity. It is important to start
at the current fitness level and steadily work up to