Just completed the W5R3 which involved a 20 min run ( with no breaks). Just last year I could barely walk 100 meters before I was short of breath and Wheezy.
I was diagnosed with brittle, badly controlled asthma- had xrays and scans to determine as to why my asthma was so bad.
I decided to take on running to challenge myself and of course get fitter - as I was really unfit. I was really frightened when I first started running that I would get an Asthma attack
What really helps is taking my inhalers ( reliever) before I start running and carrying the inhalers in my pocket, just in case I need them. I take it slow- slow jog and do not look at distance. It's all about endurance. Of course you need to speak to your doctor which doesn't apply to me as I am already a doctor- a consultant in Anaesthesia so I just follow my own judgement and instincts when running.
I have found that my Asthma has got better ( I just managed a 20 min run- I still can't believe I did it!!)
I also ski at an indoor ski slope and running has improved my endurance
So all of you out there who think you can't do it- remember if I can do it- with severe Asthma-you can definitely do it!!!!