Effects of Exercise on the Airways

In the last ten years, the effects of exercise on bronchial epithelial cells and inflammatory cells in the airways have been studied in detail, and such new information has been combined with previous knowledge on bronchial reactivity and asthma evoked by exercise in asthmatic patients and athletes. The resulting picture is very complex, and the potential clinical consequences are often contradictory, suggesting the opportunity to define different phenotypes of exercise-associated airway changes (Lee & Anderson, 1985; Haahtela et al., 2008; Moreira et al., 2011a). Studies in asthmatic athletes in the 90’ had began to explore the possibility that airway inflammation might be involved in exercise-associated respiratory symptoms. However, studies in non-asthmatic athletes also found increased number of inflammatory cells not only at rest, but also after strenuous endurance exercise (Bonsignore et al., 2001). It was therefore hypothesized that endurance exercise may physiologically cause influx of inflammatory cells into the airways, associated with low or absent inflammatory activation (Bonsignore et al., 2003a). Subsequent studies in athletes and animal models have extended these finding, but the mechanisms of inflammatory cell recruitment into the airways and the tight control of inflammatory activation physiologically associated with exercise remain poorly understood. Exercise is a known cause of bronchoconstriction in asthmatic patients (Cabral et al., 1999) and athletes (Parsons & Mastronarde, 2005). A large number of asthmatic elite athletes participate to international top-level competitions, and guidelines regarding management of asthmatic athletes (Fitch et al., 2008) and rules on the use of anti-asthmatic drugs have been issued (World Anti-Doping Agency, WADA, Oct. 18 2010 report). However, exercise is a powerful physiologic stimulus for bronchodilatation, and some reports underlined that exercise training may actually downmodulate bronchial reactivity in normal subjects (Scichilone et al., 2005, 2010), asthmatic children (Bonsignore et al., 2008) and animal models of asthma (Hewitt et al., 2010). This chapter will summarize the changes induced by acute exercise and training in bronchial reactivity and airway cells in both humans and animal models. It will also discuss the changing paradigm regarding the impact of physical activity in patients with bronchial asthma, and the new perspectives of exercise-based rehabilitation in patients with respiratory diseases such as chronic obstructive pulmonary disease (COPD).