Adequacy of Evidence for Physical Activity Guidelines Development Workshop Summary (2007) / Chapter Skim
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2 Physical Activity, Health Promotion, and Chronic Disease Prevention
2 Physical Activity, Health Promotion, and Chronic Disease Prevention
Pages 17-58
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, all-cause mortality, and cancer • Bone, joint, and muscle health and performance • Mental and neurological health • Diabetes and other metabolic disorders Brief coverage of mechanisms of action in diabetes and of physical activity and cognition appears under the discussion section, followed by points raised by participants during the group discussion. CARDIOVASCULAR DISEASE, ALL-CAUSE MORTALITY, AND CANCER Presenter: Steven N
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The objective assessment of physical activity levels, such as the use of accelerometers or specific fitness tests, is expected to provide stronger evidence of the effects of physical activity or inactivity on various health outcomes. Physical Activity, Fitness, and Cardiovascular Disease Figure 2-1 illustrates the results obtained from a study of CVD death rates for women and men by fitness category (obtained using an objective test of fitness)
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shows that, among individuals with documented coronary artery disease, the group randomly assigned to exercise (20 minutes per day on a cycle ergometer and a 60minute group aerobic exercise class once per week) had greater eventfree survival and exercise capacity than the group assigned to standard treatment and angioplasty.
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. A study of 710 asymptomatic men with a coronary artery calcium score of greater than 100 found a very large reduction in the relative risk of CHD events for those having an exercise tolerance of 10 or more METS (Lamonte et al., 2006)
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report that the inverse association of cardiorespiratory fitness with cancer mortality remains after adjustment for the percentage of body fat.
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Bone Health Many studies show positive effects of either a physically active lifestyle or exercise interventions on intermediate markers of bone health, such as BMC and BMD. The evidence regarding the effects of physical activity on the risk of osteoporosis comes from randomized controlled trials of exercise intervention, meta-analyses of those trials, trials of the effects of immobilization and unloading, observational studies, and others.
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No randomized controlled trials are available, but some prospective observational studies provide useful data about physical activity and hip fracture risk. The report by Feskanich et al.
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Thus evidence in animals suggests that physical activity or mechanical loading probably affects the skeleton in a way that translates into large gains in bone strength.
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(N) FIGURE 2-2 Effects of mechanical loading on bone mineral content, bone mineral density, ultimate force (the maximum amount of force supported before failure)
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Muscle Health In contrast with bone health and joint health, muscle health is not directly linked with a chronic disease. A few chronic diseases, however,
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Physical Activity and Muscle Mass A wealth of evidence indicates that high-intensity resistance exercise induces muscle hypertrophy and that this adaptive response is retained into very old age. Aerobic exercise has little or no anabolic effect on muscle, although disuse causes muscle atrophy.
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Whether physical activity helps to prevent the development of OA is not known, but there is moderate to strong evidence that physical activity has beneficial effects on pain and disability in people with knee OA. Aerobic exercise has little effect on the preservation of muscle mass but has multiple favorable effects on muscle quality.
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Anxiety Approximately 50 epidemiological studies address physical activity and anxiety. About 85 percent of these show less severe symptoms of anxiety among physically active adults and youth.
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Randomized controlled trial of 46 outpatients with panic disorder. SOURCE: Broocks et al.
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, randomized controlled trials (of variable quality) show antidepressant effects of exercise, and evidence suggests biologically plausible mechanisms for the preventive effects of physical activity on anxiety.
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In summary, the size of the literature is modest, but it shows that physical activity is consistently associated with both fewer self-reported sleep problems in cross-sectional studies and improved sleep quality in randomized controlled trials. Limited indirect evidence suggests biologically plausible mechanisms by which physical activity could improve sleep or prevent sleep disorders.
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Physical inactivity generally is associated with more smoking in crosssectional studies. A modest number of randomized controlled trials failed to show that increased physical activity levels lead to significant improvements in smoking cessation.
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(2004) , 10 randomized controlled trials have been conducted in older adults with cognitive impairment to examine the effect of exercise on cognitive performance.
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Five relatively small randomized controlled trials all show a positive effect of exercise training on symptoms of chronic fatigue syndrome (Fulcher and White, 1997; Moss-Morris et al., 2005; Powell et al., 2001; Wallman et al., 2004; Weardon et al., 1998)
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, and that a meta-analysis of 61 randomized controlled trials showed that exercise was more effective than usual care by the general practitioner and just as effective as conventional physical therapy for chronic low back pain (Hayden et al., 2005)
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This presentation began with background information and then covered physiological studies, observational studies, randomized controlled trials, and meta-analyses related to physical activity and type 2 diabetes mellitus. Background Diabetes is a public health problem in the United States: approximately 21 million children and adults -- 7 percent of the population -- have diabetes, but only about 14.6 million have been diagnosed (Sigal et al., 2006)
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Physical activity can attenuate adverse effects in the progression from normal glucose metabolism to clinical type 2 diabetes and various complications, as shown in Figure 2-6. In contrast, physical inactivity accelerates these unfavorable metabolic and cardiovascular events.
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provides evidence that regular moderate intensity exercise benefits cardiorespiratory fitness in persons with diabetes and that higher intensity exercise would have an even greater effect. Even a single bout of moderate exercise has a profound effect on glucose metabolism that may last up to about 18 hours (Devlin et al., 1987)
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. Randomized Controlled Trials of Type 2 Diabetes Prevention One of the earliest trials (Cederholm, 1985)
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report that body weight maintenance, insulin sensitivity and glycemic control, blood pressure, dyslipidemia, and inflammation and endothelial function all are impacted by the level of physical activity. In the Diabetes Prevention Program, the risk of developing the metabolic syndrome was lower for the lifestyle (diet and exercise)
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Dishman) Physical activity and cognition is an emerging area of study that shows much promise.
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Morrow During the group discussion, points raised by participants included the following: • Randomized controlled trials address effects of exercise on risk factors for CVD, such as blood pressure, and on mechanisms such as fibrinolytic activity and flow-mediated dilation. • Evidence regarding the acute benefits of single bouts of exercise merits consideration.
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Guidelines could focus on health promotion and disease preven tion, but probably there is sufficient evidence to focus on guid ance for people with currently active disease as well. Moreover, there is literature on interventions to help people increase their physical activity.
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1999. Effects of exercise training on oxygen uptake kinetic responses in women with type 2 diabetes mellitus.
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Risk factors for diabetes mellitus and cardiovascular disease.
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1997. Randomised controlled trial of graded exercise in patients with the chronic fatigue syndrome.
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2004. Percutane ous coronary angioplasty compared with exercise training in patients with sta ble coronary artery disease: A randomized trial.
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2004. Cardiorespiratory fitness attenuates the effects of the metabolic syndrome on all-cause and cardiovascular disease mortality in men.
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2002. Effects of moderate-intensity exercise on physiological, behavioral, and emotional re sponses to family caregiving: A randomized controlled trial.
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2002. Long-term effect of body weight-supported treadmill training in Parkinson's disease: A randomized controlled trial.
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2005. A randomized controlled graded exercise trial for chronic fatigue syndrome: Outcomes and mechanisms of change.
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2001. Randomised controlled trial of patient education to encourage graded exercise in chronic fatigue syn drome.
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Med Sci Sports Exerc 34 (5 suppl)
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2005. A randomized controlled trial of high versus low intensity weight train ing versus general practitioner care for clinical depression in older adults.
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1985. Intervention on cardiovascular disease risk factors in Finnmark county: Changes after a period of three years.
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2004. Ran domised controlled trial of graded exercise in chronic fatigue syndrome.
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1995. Incidence and risk factors of vas cular dementia and Alzheimer's disease in a defined elderly Japanese popula tion: The Hisayma Study.
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