Asthma diagnosis and treatment
Physical activity and exercise in asthma: Relevance to etiology and treatment

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There is little doubt that the cause of the increased prevalence and severity of asthma is multifactorial. Although the factors of allergen exposure and hygiene are almost certainly necessary for its development, there is a growing body of literature that implicates lifestyle change, specifically decreased physical activity, as a contributor to the increase in asthma prevalence and severity. Several literature reviews of exercise conditioning in patients with asthma have been published. These reviews and recent controlled trials emphasize that although many of the studies of exercise conditioning in asthmatic patients involved different methods and outcome measures, the overwhelming majority of studies demonstrated the capacity for asthmatic subjects to exercise safely and significantly improve their cardiovascular fitness and quality of life. There are several proposed pathophysiologic mechanisms responsible for the effects of decreased activity on the lung function of patients with asthma. A prescription for exercise has been endorsed for all asthmatic subjects by the American College of Sports Medicine and the American Thoracic Society. The allergy community has placed emphasis on medical therapy and allergen avoidance; in addition, exercise avoidance has not been formally incorporated into the National Asthma Education and Prevention Program guidelines. It is our belief that an exercise prescription should be part of the treatment for all cases of asthma. The real question is whether prolonged physical activity and, in particular, outdoor play of children plays a role in prophylaxis against persistent wheezing. If so, the decrease in physical activity might have played a major role in recent increases in asthma prevalence and severity.

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Epidemiology of the increased prevalence and severity of asthma

Asthma prevalence, severity, and hospitalization have increased over the last 4 decades. Although there seems to have been a slight plateau in asthma incidence in recent years, the prevalence remains very high, and true causes of the epidemic remain an enigma. The increase has affected many different populations, but the increase has disproportionately affected African Americans and Latinos living in poverty in the United States. By contrast, rural areas that have maintained a traditional

Allergen sensitization

There have been strong and consistent associations between aeroallergen sensitization, especially to dust mites, and asthma. Supported by bronchial challenge and avoidance studies, these are strongly suggestive of a causal relationship between sensitization and asthma.4 Subsequently, many different perennial allergens from other parts of the world have been implicated as determinants of inflammation and bronchial hyperreactivity (BHR). The hygiene hypothesis proposes that decreased exposure to

Exercise conditioning for patients with asthma

Orenstein's 2002 literature review of exercising patients with pulmonary disease concluded that asthmatic subjects can improve cardiopulmonary fitness with exercise conditioning.21 In addition to decreased risk of cardiovascular disease and diabetes, the benefits of conditioning on asthma are both subjective (increased participation in activities, improved emotional status, and decreased intensity of wheezing attacks) and objective (improved running performance and increased aerobic fitness).

Deep inspiration and smooth muscle

There are many factors influencing the patency of bronchioles (Fig 1). There has been a lot of speculation that collagen deposition or airway remodeling plays a significant role in decreased airway patency or compliance. Some authors have speculated that increased smooth muscle is the cause of excessive bronchoconstriction or changed compliance. Thomson and colleagues,31 however, evaluated cross-sectional airway muscle in axial airway sections at high resolution and found no evidence of

Exercise prescription for asthmatic subjects

Both the ACSM1 and the ATS2 guidelines recommend exercise for patients with asthma. Exercise training is the key component to pulmonary rehabilitation. The ACSM guidelines state that “current evidence suggests that the standard principles of exercise prescription (mode, frequency, intensity, and duration) can be applied to patients with respiratory diseases, including asthma.” The recommended mode of aerobic exercise is walking or any mode of aerobic exercise with large muscles. The optimal

Conclusion

There is little doubt that the cause of increased prevalence and severity of asthma is multifactorial. Although allergen exposure and some levels of hygiene might be necessary for its development, there is a growing body of literature that implicates decreased physical activity as a contributor to the increase in asthma prevalence and severity.

Exercise conditioning of asthmatic subjects has been endorsed in the literature for decades. Although it is true that fitness levels are lower among

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    Supported by National Institutes of Health grants no. AI-20565 and AI/EHS-P01-AI-50989.

    Disclosure of potential conflict of interest: T. A. E. Platts-Mills—none disclosed. S. R. Lucas—none disclosed.

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