| |
- The Effects of Physical
Activity on Health and Disease
- Physical Activity and
Health: A Report of the Surgeon General
This chapter examines the
relationship of physical activity and cardiorespiratory fitness to a variety of
health problems. The primary focus is on diseases and conditions for which
sufficient data exist to evaluate an association with physical activity, the
strength of such relationships, and their potential biologic mechanisms. Because
most of the research to date has addressed the health effects of endurance-type
physical activity (involving repetitive use of large muscle groups, such as in
walking and bicycling), this chapter focuses on that type of activity. Unless
otherwise specified, the term physical activity should be understood to refer to
endurance-type physical activity. Less well studied are the health effects of
resistance-type physical activity (i.e., that which develops muscular strength);
when this type of physical activity is discussed, it is specified as such. Much
of the research summarized is based on studies having only white men as
participants; it remains to be clarified whether the relationships described
here are the same for women, racial and ethnic minority groups, and people with
disabilities.
Physical activity is difficult to measure
directly. Three types of physical activity measures have been used in
observational studies over the last 40 years. Most studies have relied on
self-reported level of physical activity, as recalled by people prompted by a
questionnaire or interview. A more objectively measured characteristic is
cardiorespiratory fitness (also referred to as cardiorespiratory endurance)
which is measured by aerobic power (see Chapter 2 for more information on
measurement issues). Some studies have relied on occupation to classify people
according to how likely they were to be physically active at work.
Epidemiologic studies of physical activity
and health have compared the activity levels of people who have or develop
diseases and those who do not. Cohort studies follow populations forward in time
to observe how physical activity habits affect disease occurrence or death. In
case-control studies, groups of persons who have disease and separate groups of
people who do not have disease are asked to recall their previous physical
activity. Cross-sectional studies assess the association between physical
activity and disease at the same point in time. Clinical trials, on the other
hand, attempt to alter physical activity patterns and then assess whether
disease occurrence is modified as a result.
Results from epidemiologic studies can be
used to estimate the relative magnitude or strength of an association between
physical activity and a health outcome. Two such measures used in this chapter
are risk ratio (RR) and odds ratio (OR). For these measures, an estimate of 1.0
indicates no association, when the risk of disease is equivalent in the two
groups being compared. RR or OR estimates greater than 1.0 indicate an increase
in risk; those less than 1.0 indicate a decreased risk. Confidence intervals
(CI) reported with estimates of association indicate the precision of the
estimate, as well as its statistical significance. When the CI range includes
1.0, the effect is considered likely to have occurred by chance; therefore the
estimate of association is not considered statistically significantly different
from the null value of 1.0.
Conclusions
Overall Mortality
- Higher levels of regular physical
activity are associated with lower mortality rates for both older and
younger adults.
- Even those who are moderately active
on a regular basis have lower mortality rates than those who are least
active.
Cardiovascular Diseases
- Regular physical activity or
cardiorespiratory fitness decreases the risk of cardiovascular disease
mortality in general and of coronary heart disease mortality in
particular. Existing data are not conclusive regarding a relationship
between physical activity and stroke.
- The level of decreased risk of
coronary heart disease attributable to regular physical activity is
similar to that of other lifestyle factors, such as keeping free from
cigarette smoking.
- Regular physical activity prevents or
delays the development of high blood pressure, and exercise reduces blood
pressure in people with hypertension.
Cancer
- Regular physical activity is
associated with a decreased risk of colon cancer.
- There is no association between
physical activity and rectal cancer. Data are too sparse to draw
conclusions regarding a relationship between physical activity and
endometrial, ovarian, or testicular cancers.
- Despite numerous studies on the
subject, existing data are inconsistent regarding an association between
physical activity and breast or prostate cancers.
Non-Insulin-Dependent Diabetes Mellitus
- Regular physical activity lowers the
risk of developing non-insulin-dependent diabetes mellitus.
Osteoarthritis
- Regular physical activity is
necessary for maintaining normal muscle strength, joint structure, and
joint function. In the range recommended for health, physical activity is
not associated with joint damage or development of osteoarthritis and may
be beneficial for many people with arthritis.
- Competitive athletics may be
associated with the development of osteoarthritis later in life, but
sports-related injuries are the likely cause.
Osteoporosis
- Weight-bearing physical activity is
essential for normal skeletal development during childhood and adolescence
and for achieving and maintaining peak bone mass in young adults.
- It is unclear whether resistance- or
endurance-type physical activity can reduce the accelerated rate of bone
loss in postmenopausal women in the absence of estrogen replacement
therapy.
Falling
- There is promising evidence that
strength training and other forms of exercise in older adults preserve the
ability to maintain independent living status and reduce the risk of
falling.
Obesity
- Low levels of activity, resulting in
fewer kilocalories used than consumed, contribute to the high prevalence
of obesity in the United States.
- Physical activity may favorably
affect body fat distribution.
Mental Health
- Physical activity appears to relieve
symptoms of depression and anxiety and improve mood.
- Regular physical activity may reduce
the risk of developing depression, although further research is required
on this topic.
Health-Related Quality of Life
- Physical activity appears to improve
health-related quality of life by enhancing psychological well-being and
by improving physical functioning in persons compromised by poor health.
Adverse Effects
- Most musculoskeletal injuries related
to physical activity are believed to be preventable by gradually working
up to a desired level of activity and by avoiding excessive amounts of
activity.
- Serious cardiovascular events can
occur with physical exertion, but the net effect of regular physical
activity is a lower risk of mortality from cardiovascular disease.
Centers for Disease Control and Prevention
National Center for Chronic Disease Prevention and Health Promotion
Division of Cancer Prevention and Control
Path:
Home>Education>Fitness
and Physical Activity Information>Physical
Activity and Your Health: The Effects of Physical Activity on Health and Disease
|
|
