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Feb 8, 2012

Lack of sufficient physical activity is the second most important contributor to preventable deaths, trailing only tobacco use. A sedentary lifestyle has been linked to 28% of deaths from leading chronic diseases. The US Department of Health and Human Services and Centers for Disease Control and Prevention (CDC) recommends that adults and older adults engage in 150 minutes of moderate-intensity (such as brisk walking) or 75 minutes of vigorous-intensity aerobic activity (such as jogging or running) or an equivalent mix of moderate- and vigorous-intensity aerobic activity each week. In addition to the activity recommendations, the CDC recommends activities to strengthen all major muscle groups (abdomen, arms, back, chest, hips, legs, and shoulders) at least twice a week. Patients who engage in regular moderate to vigorous exercise have a lower risk of myocardial infarction, stroke, hypertension, hyperlipidemia, 2 diabetes mellitus, diverticular disease, and osteoporosis.

Evidence supports the recommended guidelines of 30 minutes of moderate physical activity on most days of the week in both the primary and secondary prevention of CHD. In older nonsmoking men, walking 2 miles or more per day is associated with an almost 50% lower age-related mortality. The relative risk of stroke was found to be less than one-sixth in men who exercised vigorously compared with those who were inactive; the risk of type 2 diabetes mellitus was about half among men who exercised five or more times weekly compared with those who exercised once a week. Glucose control is improved in diabetics who exercise regularly, even at a modest level. In sedentary individuals with dyslipidemia, high amounts of high-intensity exercise produce significant beneficial effects on serum lipoprotein profiles. Physical activity is associated with a lower risk of colon cancer (although not rectal cancer) in men and women and of breast and reproductive organ cancer in women. Finally, weight-bearing exercise (especially resistance and high-impact activities) increases bone mineral content and retards development of osteoporosis in women and contributes to a reduced risk of falls in older persons.

Resistance training has been shown to enhance muscular strength, functional capacity, and quality of life in men and women with and without CHD and is endorsed by the American Heart Association. Exercise may also confer benefits on those with chronic illness. Men and women with chronic symptomatic osteoarthritis of one or both knees benefited from a supervised walking program, with improved self-reported functional status and decreased pain and use of pain medication. Exercise produces sustained lowering of both systolic and diastolic blood pressure in patients with mild hypertension. In addition, physical activity can help patients maintain ideal body weight. Individuals who maintain ideal body weight have a 35–55% lower risk for myocardial infarction than with those who are obese. Physical activity reduces depression and anxiety; improves adaptation to stress; improves sleep quality; and enhances mood, self-esteem, and overall performance. In longitudinal cohort studies, individuals who report higher levels of leisure time physical activity are less likely to gain weight. Conversely, individuals who are overweight are less likely to stay active. However, at least 60 minutes of daily moderate-intensity physical activity may be necessary to maximize weight loss and prevent significant weight regain. Moreover, adequate levels of physical activity appear to be important for the prevention of weight gain and the development of obesity.

Physical activity also appears to have an independent effect on health-related outcomes such as development of type 2 diabetes mellitus in patients with impaired glucose tolerance when compared with body weight, suggesting that adequate levels of activity may counteract the negative influence of body weight on health outcomes. Only about 20% of adults in the United States are active at the moderate level—and only 8% currently exercise at the more vigorous level—recommended for health benefits. Instead, 60% report irregular or no leisure time physical activity. Increased activity increases the risk of musculoskeletal injuries, which can be minimized by proper warm-up and stretching and by gradual rather than sudden increase in activity. In insulin-requiring diabetic patients who undertake vigorous exercise, the need for insulin is reduced; hypoglycemia may be a consequence. Physical exertion can rarely trigger the onset of acute myocardial infarction, particularly in persons who are habitually sedentary. Other potential complications of exercise include angina pectoris, arrhythmias, sudden death, and asthma.

The value of routine electrocardiography stress testing prior to initiation of an exercise program in middle-aged or older adults remains controversial. Patients with ischemic heart disease or other cardiovascular disease require medically supervised, graded exercise programs. Medically supervised exercise prolongs life in patients with congestive heart failure. Exercise should not be prescribed for patients with decompensated congestive heart failure, complex ventricular arrhythmias, unstable angina pectoris, hemodynamically significant aortic stenosis, or significant aortic aneurysm. Five- to 10-minute warm-up and cool-down periods, stretching exercises, and gradual increases in exercise intensity help prevent musculoskeletal and cardiovascular complications.

McPhee, Stephen; Papadakis, Maxine; Rabow, Michael W.. CURRENT Medical Diagnosis and Treatment 2012, Fifty-First Edition (Kindle Locations 2106-2141). McGraw-Hill. Kindle Edition.


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