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Summary:
The benefits of physical activity have been extolled throughout
western history, but it was not until the second half of this
century that scientific evidence supporting these beliefs
began to accumulate. By the 1970s, enough information was
available about the beneficial effects of vigorous exercise
on cardiorespiratory fitness that the American College of
Sports Medicine (ACSM), the American Heart Association (AHA),
and other national organizations began issuing physical activity
recommendations to the public. These recommendations generally
focused on cardiorespiratory endurance and specified sustained
periods of vigorous physical activity involving large muscle
groups and lasting at least 20 minutes on 3 or more days per
week.
As
understanding of the benefits of less vigorous activity grew,
recommendations followed suit. During the past few years,
the ACSM, the CDC, the AHA, the PCPFS, and the NIH have all
recommended regular, moderate-intensity physical activity
as an option for those who get little or no exercise. The
Healthy People 2000 goals for the nation's health have recognized
the importance of physical activity and have included physical
activity goals. The 1995 Dietary Guidelines for Americans,
the basis of the federal government's nutrition-related programs,
included physical activity guidance to maintain and improve
weight - 30 minutes or more of moderate-intensity physical
activity on all, or most, days of the week. Underpinning such
recommendations is a growing understanding of how physical
activity affects physiologic function.
The body responds to physical activity in ways that have important
positive effects on musculoskeletal, cardiovascular, respiratory,
and endocrine systems. These changes are consistent with a
number of health benefits, including a reduced risk of premature
mortality and reduced risks of coronary heart disease, hypertension,
colon cancer, and diabetes mellitus. Regular participation
in physical activity also appears to reduce depression and
anxiety, improve mood, and enhance ability to perform daily
tasks throughout the life span. The risks associated with
physical activity must also be considered. The most common
health problems that have been associated with physical activity
are musculoskeletal injuries, which can occur with excessive
amounts of activity or with suddenly beginning an activity
for which the body is not conditioned. Much more serious associated
health problems (i.e., myocardial infarction, sudden death)
are also much rarer, occurring primarily among sedentary people
with advanced atherosclerotic disease who engage in strenuous
activity to which they are unaccustomed.
Sedentary
people, especially those with preexisting health conditions,
who wish to increase their physical activity should therefore
gradually build up to the desired level of activity. Even
among people who are regularly active, the risk of myocardial
infarction or sudden death is somewhat increased during physical
exertion, but their overall risk of these outcomes is lower
than that among people who are sedentary. Research on physical
activity continues to evolve.
This
report includes both well-established findings and newer research
results that await replication and amplification. Interest
has been developing in ways to differentiate between the various
characteristics of physical activity that improve health.
It remains to be determined how the interrelated characteristics
of amount, intensity, duration, frequency, type, and pattern
of physical activity are related to specific health or disease
outcomes. Attention has been drawn recently to findings from
three studies showing that cardiorespiratory fitness gains
are similar when physical activity occurs in several short
sessions (e.g., 10 minutes) as when the same total amount
and intensity of activity occurs in one longer session (e.g.,
30 minutes). Although, strictly speaking, the health benefits
of such intermittent activity have not yet been demonstrated,
it is reasonable to expect them to be similar to those of
continuous activity. Moreover, for people who are unable to
set aside 30 minutes for physical activity, shorter episodes
are clearly better than none. Indeed, one study has shown
greater adherence to a walking program among those walking
several times per day than among those walking once per day,
when the total amount of walking time was kept the same. Accumulating
physical activity over the course of the day has been included
in recent recommendations from the CDC and ACSM, as well as
from the NIH Consensus Development Conference on Physical
Activity and Cardiovascular Health.
Despite
common knowledge that exercise is healthful, more than 60
percent of American adults are not regularly active, and 25
percent of the adult population are not active at all. Moreover,
although many people have enthusiastically embarked on vigorous
exercise programs at one time or another, most do not sustain
their participation. Clearly, the processes of developing
and maintaining healthier habits are as important to study
as the health effects of these habits. The effort to understand
how to promote more active lifestyles is of great importance
to the health of this nation.
Although the study of physical activity determinants and interventions
is at an early stage, effective programs to increase physical
activity have been carried out in a variety of settings, such
as schools, physicians' offices, and worksites. Determining
the most effective and cost-effective intervention approaches
is a challenge for the future. Fortunately, the United States
has skilled leadership and institutions to support efforts
to encourage and assist Americans to become more physically
active. Schools, community agencies, parks, recreational facilities,
and health clubs are available in most communities and can
be more effectively used in these efforts. School-based interventions
for youth are particularly promising, not only for their potential
scope - almost all young people between the ages of 6 and
16 years attend school - but also for their potential impact.
Nearly half of young people 12-21 years of age are not vigorously
active; moreover, physical activity sharply declines during
adolescence. Childhood and adolescence may thus be pivotal
times for preventing sedentary behavior among adults by maintaining
the habit of physical activity throughout the school years.
School-based interventions have been shown to be successful
in increasing physical activity levels. With evidence that
success in this arena is possible, every effort should be
made to encourage schools to require daily physical education
in each grade and to promote physical activities that can
be enjoyed throughout life.
Outside the school, physical activity programs and initiatives
face the challenge of a highly technological society that
makes it increasingly convenient to remain sedentary and that
discourages physical activity in both obvious and subtle ways.
To increase physical activity in the general population, it
may be necessary to go beyond traditional efforts. This report
highlights some concepts from community initiatives that are
being implemented around the country. It is hoped that these
examples will spark new public policies and programs in other
places as well. Special efforts will also be required to meet
the needs of special populations, such as people with disabilities,
racial and ethnic minorities, people with low income, and
the elderly. Much more information about these important groups
will be necessary to develop a truly comprehensive national
initiative for better health through physical activity. Challenges
for the future include identifying key determinants of physically
active lifestyles among the diverse populations that characterize
the United States (including special populations, women, and
young people) and using this information to design and disseminate
effective programs.
source,
United States Government
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LIVING STRONG ARTICLE LIBRARY