Exercise is any physical activity that involves planned, structured, and repeated movements of the body to improve or maintain physical fitness. This usually involves both aerobic activities that improve cardiovascular fitness and strength training of the body's muscles. Exercise for disease prevention means performing enough physical activity to keep the body healthy and help avoid many serious illnesses, such as heart disease, diabetes, and some types of cancer.
As people become more busy and as they rely more on technology to help with daily activities, they become more sedentary (less active). For example, man used to have to walk to gather food, or at least into town to a store. People moved about more in their jobs and at home. Many people now use computers at work all day and then use them at home in the evening or spend hours watching television. They rely on automobiles for errands, such as food shopping or visiting family members. Because people move less often naturally, they must rely more on planned exercise to keep muscles working and to balance all of the calories taken in with the energy the body uses up. This is one reason why obesity has been on the rise in the United States for the past 20 years. According to the U.S. Centers for Disease Control and Prevention, one-third (33%) of American adults are obese and 17% of children and teens are obese.
Obesity is a factor in health and disease, and exercise can help fight obesity and its associated health problems. A study reported that people in certain regions of the country were most active in their spare time. Those who live on the West Coast and in the states of Minnesota and Colorado are the most active. On the other hand, people who live in Appalachia and the South are the least active. Estimated levels of obesity and diabetes also are higher in the South and parts of Appalachia. The diseases are the lowest in the West and the Northeast.
Exercise ranges from regular walks or bike rides to participation in team or competitive sports. Some of the best exercises for disease prevention are brisk walking, bicycling, jogging, hiking, swimming, yoga, aerobics classes, martial arts, and using gyms and fitness centers. To maintain general health, an exercise program should include aerobic and strength, or resistance, training programs. The U.S. Department of Health and Human Service's “Physical Activity Guidelines for Americans,” issued in 2008, suggest at least two hours and 30 minutes a week of moderate-intensity exercise (such as brisk walking). They also suggest some sort of muscle-strengthening activity. Disease prevention benefits increase with more time, higher intensity, and more frequent exercise.
When calculating health benefits of exercise and how much people need to participate in to prevent disease, it helps to translate the activity into energy. Exercise expends, or uses, energy. This is one reason why people often must organize exercise activities in modern times to replace the energy once used walking, chopping wood for fuel, and doing other tasks we no longer have to do thanks to innovations. A metabolic equivalent, or MET, is a unit that can help compare how much energy one activity expends compared with another. The committee that came up with the federal fitness guidelines determined that Americans needed 500 to 1,000 MET-minutes of activity per week for health benefits from exercise. They assigned levels of intensity as well, so that a person could exercise at a higher intensity for a shorter period of time or at a lower intensity for more time and achieve nearly equal health benefits. Moderate-intensity activity is defined as 5 to 6 on a 10-point scale in which sitting still is rated as 0 effort and 10 is maximum effort. These calculations helped to arrive at the 150-minute-per week recommendation for preventing disease with physical activity. Longer or more intense activity can provide more benefits and any activity is better than none.
The fitness recommendations are meant to help prevent disease and recognize what physicians know: that regular physical activity can improve general wellbeing. Although the role of exercise in preventing disease might not always be understood, it has been shown to help people sleep better, reduce stress, improve mood, and control weight. All of these factors improve health, along with the ways exercise helps prevent specific diseases.
Cardiovascular disease is one of the biggest problems among Americans. High blood pressure, strokes, heart attacks, and coronary artery disease contribute to death and poor quality of life, and more than 2,200 Americans each day die from cardiovascular diseases. Other factors contribute to the risk of developing these diseases, but regular exercise helps combat this risk. Studies that link the benefits of exercise in lowering risk of heart disease date back to the 1940s. Even one hour of brisk walking a week can lower risk, but more activity is better. Inactivity adds to risk of high blood pressure, so becoming active greatly reduces blood pressure. It also helps reduce the buildup of plaque in the arteries (coronary artery disease) that can lead to strokes. Exercise makes arteries healthier because when people exercise, their arteries expand and contract. This helps the arteries fight plaque buildup. The American Heart Association recommends at least 150 minutes of moderate activity or 75 minutes of vigorous activity a week, along with strengthening exercises involving at least two major muscle groups at least two days a week to fight cardiovascular disease.
Ideas about the positive link between exercise and cancer have been around for centuries. It's only in the past 10 or 20 years, however, that scientists have been able to prove the link. A study in the Journal of the American Medical Association reported that moderate exercise can double survival rates of women with breast cancer. Most research has looked at how exercise throughout life lowers risk of colorectal cancer. A study on women specifically showed that women who exercise when they are middle-aged (three hours of intense activity or four hours of moderate activity a week) can lower their risk of colorectal cancer.
As mentioned earlier, weight-bearing exercise lowers risk or severity of osteoporosis. Exercise helps ease the symptoms and pain associated with rheumatoid arthritis and osteoarthritis. Regular moderate exercise and weight control can help prevent or delay onset of osteoarthritis. Exercise can strengthen the immune system and can help fight off colds and other viruses. Pregnant women benefit from exercise, and it has been shown to improve the health of their babies' hearts after the babies are born. A link has been found between exercise and gallstones. Excess weight adds to risk of gallstones and exercise also may prevent the stones. Studies even have found that exercise can help prevent Alzheimer's disease. A recent report noted that people who exercised by walking or cycling at least twice a week in middle age were 60% less likely to have the form of dementia when they got older. Finally, exercise has been shown to help control and fight mood disorders such as depression and anxiety. Moderate exercise helps reduce the number of symptoms people with depression have. Exercise also is prescribed to help treat depression in some cases.
Although most disease prevention is only improved with increased exercise intensity and duration, exercise can be harmful if done incorrectly. People who have not exercised in the past should not begin an exercise program without the guidance of their physicians, especially if they have a disease or are overweight or obese. Studies show that people are more likely to stick to exercise programs when they enjoy the activities, so it also helps to work with doctors or other professionals to find exercise activities that are enjoyable and not painful. A doctor may perform a physical examination on a person who is preparing to begin a new exercise program and recommend frequency and types of activities aimed at reducing specific disease risks, along with how to gradually increase intensity.
People choosing to exercise to prevent disease also have to recognize that exercise can only do so much. For example, a person who exercises but continues smoking will not experience the same prevention effects for cardiovascular disease as someone who exercises and quits smoking. Exercising with high-impact activities can even increase risk for some diseases. For example, running can improve cardiovascular fitness but increase chance of fracture risk in bones or repeated injury to joints that can lead to osteoarthritis. Finally, people should realize that any increase in physical activity is an improvement, even though the goal is to increase exercise to the levels that can prevent disease. Because time is one of the most cited factors for failing to exercise, it is not helpful to begin an exercise program and then quit all physical activity because time is too much of an issue. It is better to get in as much activity and exercise as possible than to be inactive, even if the time spent exercising is less than recommended amounts.
See also Cardiovascular disease ; Exercise .
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President's Council on Fitness, Sports & Nutrition, 1101 Wootton Pkwy., Ste. 560, Rockville, MD, 20852, (240) 276-9567, Fax: (240) 276-9860, email@example.com, http://www.presidentschallenge.org .
Teresa G. Odle, BA, ELS