I have been an asthmatic since
2010, and had only a few crisis since then. I have been active, ran 13 marathons since then, and overall asthma hasn't been a bigger issue. I control it with Symbicort twice a day and, sometimes, but rarely, Ventolin.
Last year, I felt that I wasn't breathing my best, and the doctor told me that I should take it easy on my runs and gave me this device (PFM - Peak Flow meter) where I blow to measure how good I am breathing.