Chapter 2: Historical Background and Evolution of Physical
- Physical activity for better health and well-being has been an important theme throughout much of western history.
- Public health recommendations have evolved from emphasizing vigorous activity for cardiorespiratory fitness to including the option of moderate levels of activity for numerous health benefits.
- Recommendations from experts agree that for better health, physical activity should be performed regularly. The most recent recommendations advise people of all ages to include a minimum of 30 minutes of physical activity of moderate intensity (such as brisk walking) on most, if not all, days of the week. It is also acknowledged that for most people, greater health benefits can be obtained by engaging in physical activity of more vigorous intensity or of longer duration.
- Experts advise previously sedentary people embarking on a physical activity program to start with short durations of moderate-intensity activity and gradually increase the duration or intensity until the goal is reached.
- Experts advise consulting with a physician before beginning a new physical activity program for people with chronic diseases, such as cardiovascular disease and diabetes mellitus, or for those who are at high risk for these diseases. Experts also advise men over age 40 and women over age 50 to consult a physician before they begin a vigorous activity program.
- Recent recommendations from experts also suggest that cardiorespiratory endurance activity should be supplemented with strength-developing exercises at least twice per week for adults, in order to improve musculoskeletal health, maintain independence in performing the activities of daily life, and reduce the risk of falling.
Chapter 3: Physiologic Responses and Long-Term Adaptations to Exercise
- Physical activity has numerous beneficial physiologic effects. Most widely appreciated are its effects on the cardiovascular and musculoskeletal systems, but benefits on the functioning of metabolic, endocrine, and immune systems are also considerable.
- Many of the beneficial effects of exercise training - from both endurance and resistance activities - diminish within 2 weeks if physical activity is substantially reduced, and effects disappear within 2 to 8 months if physical activity is not resumed.
- People of all ages, both male and female, undergo beneficial physiologic adaptations to physical activity.
Chapter 4: The Effects of Physical Activity on Health and Disease
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
Chapter 5: Patterns and Trends in Physical Activity
- Approximately 15 percent of U.S. adults engage regularly (3 times a week for at least 20 minutes) in vigorous physical activity during leisure time.
- Approximately 22 percent of adults engage regularly (5 times a week for at least 30 minutes) in sustained physical activity of any intensity during leisure time.
- About 25 percent of adults report no physical activity at all in their leisure time.
- Physical inactivity is more prevalent among women than men, among blacks and Hispanics than whites, among older than younger adults, and among the less affluent than the more affluent.
- The most popular leisure-time physical activities among adults are walking and gardening or yard work.
Adolescents and Young Adults
- Only about one-half of U.S. young people (ages 12-21 years) regularly participate in vigorous physical activity. One-fourth report no vigorous physical activity.
- Approximately one-fourth of young people walk or bicycle (i.e., engage in light to moderate activity) nearly every day.
- About 14 percent of young people report no recent vigorous or light to moderate physical activity. This indicator of inactivity is higher among females than males and among black females than white females.
- Males are more likely than females to participate in vigorous physical activity, strengthening activities, and walking or bicycling.
- Participation in all types of physical activity declines strikingly as age or grade in school increases.
- Among high school students, enrollment in physical education remained unchanged during the first half of the 1990s. However, daily attendance in physical education declined from approximately 42 percent to 25 percent.
- The percentage of high school students who were enrolled in physical education and who reported being physically active for at least 20 minutes in physical education classes declined from approximately 81 percent to 70 percent during the first half of this decade.
- Only 19 percent of all high school students report being physically active for 20 minutes or more in daily physical education classes.
Chapter 6: Understanding and Promoting Physical Activity
- Consistent influences on physical activity patterns among adults and young people include confidence in one's ability to engage in regular physical activity (e.g., self-efficacy), enjoyment of physical activity, support from others, positive beliefs concerning the benefits of physical activity, and lack of perceived barriers to being physically active.
- For adults, some interventions have been successful in increasing physical activity in communities, worksites, and health care settings, and at home.
- Interventions targeting physical education in elementary school can substantially increase the amount of time students spend being physically active in physical education class.
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