The effects of physical activity on asthma have been explored extensively. Exercise can trigger later bronchoconstriction in many patients, and deconditioning due to a sedentary lifestyle may be the consequence. However, the immediate effect of physical activity in asthma and health is bronchodilation. To date, little is known about the association between physical activity and lung function in the daily life of asthma patients.
We studied 20 individuals with asthma and 20 control subjects using an electronic diary of activities and spirometry (peak expiratory flow [PEF], FEV1). Participants rated their shortness of breath and their intensity of physical and social activity for the preceding 30 min. Assessments were made over the course of 3 weeks, tid (morning, afternoon, evening/night).
Stronger physical activity was concurrently associated with significantly higher lung function. In contrast, it also showed a positive concurrent association with shortness of breath. In prospective cross-lag analyses, lower PEF and FEV1 earlier in the day predicted lower physical and social activity levels later in the day, but shortness of breath did not.
The findings show that detrimental effects observed in exercise-induced bronchoconstriction cannot be generalized to physical activity in daily lives of individuals with asthma. Nevertheless, people with asthma still feel more shortness of breath when being more physically active. They adjust their activity levels throughout the day according to their earlier lung function, but this does not fully explain the concurrent positive association of physical activity and lung function.