Introduction
Asthma is a chronic disease characterized by airway inflammation and diagnosed if a subject has a history of respiratory symptoms such as wheezing, shortness of breath, chest tightness, and coughing as well as variable airflow obstruction (1). Airflow obstruction can often be reversed either spontaneously or with pharmacological treatment (1). However, approximately 10% of infant subjects with asthma in a previous study exhibited an expiratory airflow limitation that was not completely reversible, despite optimal treatment being provided (2); this condition is known as fixed airflow obstruction (FAO) (3).
FAO is diagnosed when a subjects’ ratio of the forced expiratory volume in the 1st second (FEV1) to the forced vital capacity (FVC) (FEV1/FVC) is below the lower limit of the normal range (LLN) after optimal treatment (3). The development of FAO has been explained by a type of pathological airway remodeling that leads to structural changes in the airway and airflow restrictions (4). The risk factors for FAO are multifactorial and differ between adults and children (2, 5). The main risk factors for FAO in adults include a subjects’ sex, his or her smoking habits, the presence of rhinitis, atopy, and eosinophil inflammation; and the amount of fractional exhaled nitric oxide (5). In children and adolescents, the risk factors are related to asthma severity and the frequency of exacerbations (2).
Previous studies have reported that subjects with FAO exhibit higher asthma hospitalization rates and more severe symptoms such as dyspnea, wheezing, and chest tightness than do their non-FAO peers (2, 4). The fear of feeling asthma symptoms could inhibit many subjects from taking part in regular physical activity due to exercise-induced bronchoconstriction (6). The current guidelines encourage subjects with asthma to engage in regular physical activity (1). An increase in a subject physical activity level (PAL) improves his or her aerobic fitness and health-related quality of life (HRQoL) and reduces the need for inhaled corticosteroids, asthma exacerbations, and dyspnea symptoms (7). In addition, adolescents with asthma who remain physically active exhibit a slower annual decline in the FEV1 and FEV1/FVC ratio values than do those who are physically inactive (8). Although the benefits of regular physical activity are well known, adults with asthma and FAO are physically inactive and exhibit low levels of aerobic fitness (8, 9); however, the effects of FAO in adolescents with asthma remain poorly known.
In the present study, we hypothesized that adolescents with asthma and FAO have lower levels of aerobic fitness, PAL, muscle strength, and HRQoL than do their peers with asthma but without FAO. Our study aimed to compare adolescents with FAO and their non-FAO peers in terms of aerobic fitness, PAL, muscle strength, and HRQoL.